Just before noon on Tuesday, after a month of preparation between Colorado, California, and the U.S. Consulate General in Tijuana, two U.S. foreign service officers quietly arrived at a women's shelter on the outskirts of the Mexican city. They were there to retrieve an American woman who had disappeared more than eight years ago. She was placed in a ambulance and driven 20 minutes to the border crossing of San Ysidro, where she was picked up on the American side by doctors from San Diego.

Sara, now 48, was diagnosed with several mental-health disorders in her late teens. It’s still unclear how she survived so long on the streets of Tijuana, or why she went there in the first place. But it’s clear that she never would have been found without the incredible efforts of a sister and two strangers—one a Colorado cop on the verge of retirement, and the other a young foreign service officer who put the final pieces of the puzzle together.

When Celeste Shaw was growing up in Colorado Springs, she and Sara, her younger sister, were inseparable. Sara had a sweet personality, and by the time she hit high school the strawberry-blond beauty was one of the most popular girls at school. (Sara’s first name has been changed to protect her sister’s wish to protect her identity.)

“She was super sweet and kind,” Shaw says. “Boys liked her.

But by the end of high school, Sara, who once excelled in academics, gymnastics, and volleyball, had changed. The once soft-spoken teen grew moody, began partying excessively, and became prone to violent outbursts. After a gap year, Sara started college, but dropped out by the end of her first year.

“By the time she got out of college, she started exhibiting behaviors,” recalls Shaw, now a mortgage investigator. “She was hearing voices. She thought songs on the radio were about her. When we brought her home from college, she started beating herself up. She would hit herself in the legs, torso, and sometimes in the face. We could hear her in her room. She would be yelling. She was hitting someone and the only person in the room was her.”

Her family took her to a state hospital where she was diagnosed as bipolar, schizophrenic, and suffering from schizoaffective disorder, a condition characterized by hallucinations, delusions and abnormal emotional responses and put on medication, but “nothing got better.”

Sara didn’t like staying on her medication. “A lot of the medication made her feel nothing,” said Shaw. “She couldn’t think of a thought too long. Even to feel, even if it’s bad, is better than being in this zombie-like state.”

The next two decades of Sara’s life were filled with short stays at state mental institutions, run-ins with the law, homelessness, and alcohol and drug addiction. She would also vanish for days or sometimes weeks at a time.

So when Sara disappeared in March of 2005, Shaw and her family were concerned but expected to hear from her soon. At the end of April, Sara called her sister asking her for money. She was in Tijuana and needed some cash to return home. Shaw wired money to a bank in Tijuana. However, her sister called her back and said the money never arrived. Shaw said she would find out what went wrong, and asked her sister to call her back. Sara never did.

Shaw filed a missing persons report with the Colorado Springs Police Department and contacted the American consulate in Tijuana. “Nothing came of it.”

“The consulate said if she is in jail or a state mental institution Mexican officials would call them,” she says. “They won’t pay for Americans and will get a hold of the consulate really fast.”

They recommended that she not venture to Mexico in search of her sister just in case she met foul play.

She was equally disappointed with the police. “When you file a missing person’s report, no one looks for them,” she said. “The information is there just in case a body shows up and they can ID it. Only the family looks for them. There is no known resource out there. You reinvent the wheel every time. No one will talk to you or educate you. You have to figure it out on your own.”

That’s just what Shaw did. Using her skills as an investigator, she began scouring the Internet and searching engine databases for any clues of her sister’s whereabouts. She would regularly call police departments and hospitals in the hope Sara would eventually turn up.

Eventually, she said, her search became a recovery mission, and she began contacting coroner departments in every county along the Mexican border from California to Texas looking for her sister’s remains.

“I probably looked at over 7,000 dead bodies,” she said. “I became my own expert to determine if a corpse fit the profile of my sister. The longer it went on, the harder it was. At the beginning you wonder if she is cold or hungry. The probability of her being found alive is less and less and your thoughts just shift to, ‘I hope she didn’t suffer when she died or I wonder where her body is?”

“I didn’t know how a single white female could survive on the streets of Tijuana,” she added. “There was just no help.”

Little did Shaw know at the time there was someone who was interested in Sara’s case. Colorado Springs Police Department detective Ron Lopez was working a fugitive task force when he was reassigned to take over the department’s cold case missing persons/homicide unit in 2009.

It was a daunting task.

“I looked at over 1,000 missing persons cases,” he said. “The old missing persons cases weren’t even being looked at before. On all of these cases you didn’t know if they met foul play.”

Lopez said that 80 percent of the cases turned out well. The missing person returned home or was found. He focused his attention towards those cases he believed the person may have met an untimely end. Sara was one of those cases.

Lopez scoured police databases looking for Sara and entered her profile and photo into the National Missing and Unidentified Persons System (NamUs), a national repository for information about missing and unidentified persons as well as unidentified living individuals whose identity is unknown due to circumstances such as dementia or incapacitation, gathered her dental records from her childhood dentist and her fingerprints from an earlier arrest, and contacted the American consulate in Tijuana to inform them about Sara’s last known whereabouts and the then newly created missing person database.

“We thought something bad happened to her,” said Lopez. “Living on the streets anywhere is not safe, but living on the streets in Mexico is even worse.”

Over the years, there were numerous dead ends, coincidences, and red herrings to befall him; in late June of 2013 he came across two bodies whose dental records were similar to Sara’s. He sent the dental remains to a forensic dentist, but once again there was no match.

“I was bummed but then all of a sudden I got a call from the U.S. consulate,” he said.

Enter Kevin Brosnahan. A foreign service officer with the American consulate in Tijuana, Brosnahan said he received a telephone call from a volunteer at a church in Tijuana on July 3 informing him that his church had taken a homeless woman to a shelter for women in the outskirts of the city in December of 2012 and they thought the woman might be American. The woman barely spoke Spanish and would hardly utter a word to the staff. She was in very bad shape and had a large scar across her face like she had been in a violent fight.

“At the time they had been acquainted with her for a couple of months but she didn’t know her name or any member of her family,” he said. “She was homeless for a number of years in Tijuana and church members had become acquainted with her and wanted to arrange help for her. Our understanding is that she came to the facility with no possessions and just the clothes on her back.”

Brosnahan and his colleagues went to the shelter on July 12 to find out if the homeless woman was indeed American. At first, she told them she was from France. “I asked her where in France and she said Paris,” he said. That’s when Brosnahan pulled out a map of the U.S. and asked her to point out Paris on the map. “She pointed directly to Colorado,” he said. He asked her if she had lived in Colorado, and she provided yet another clue. “She seemed to indicate she had worked at Stapleton Air Freight,” he said. “Stapleton airport was the old airport in Denver that closed in 1995. We took some clues back to the office after an hour. “

Back in his office, Brosnahan began searching NamUs for women missing in Colorado. Spending his after-work hours combing the database, looking at over 50 profiles, he came across the profile of Sara that Lopez had entered three years earlier.

“That was the only one that appeared reasonably close, he said. “ I thought this is wishful thinking on my part. My first colleague said ‘I just got chills. I think that’s her’ and my boss said, ‘That’s her.’ It made me feel better that it wasn’t wishful thinking after three hours bleary eyed on a database.”

Brosnahan called Lopez three days later and told him he tentatively had a match. Lopez asked him to send over a picture of the homeless woman. Lopez was shocked to see it. “It was her,” he said. “It looked like she was aged from living on the street.”

Celeste Shaw was on a family trip celebrating her parent’s 50th wedding anniversary when she received a call from Lopez. “He said we found her and he paused, and I thought he was going to say we found her body. When he told us she was alive my body collapsed and I fell to my knees.”

“He sent us proof,” she said. “She looked so old. She looked like she suffered a lot.”

Sara is currently at a psych ward in San Diego. “She is an American again,” says Shaw.

Shaw says once professionals assess Sara’s condition, she plans to have her sister flown back to Colorado so she could be close to her family. “I want to take care of her,” she says. “She’s my sister. She was mentally ill when she left and she needs help whether she knows it or not. She is family and if her body was somewhere I wanted it home and if she was alive I want her with family. That is what drove me. If I was missing I would want to be found.”

For Lopez, who retired last Friday, it was the perfect end to a 32-year career in law enforcement. “[Sara] has been blessed by god to be alive,” he says. “We did not expect that at all. God’s angels have watched over her.”

“It is smiles all around,” says Brosnahan. “It makes you think on that day I loved my job. Not all cases come out with a happy ending. This is beyond a happy ending.”