Story highlights The body was discovered during a routine quarterly check, officials say

Lynne Spalding went missing from San Francisco General Hospital

went missing from San Francisco General Hospital She was last seen in her hospital room on September 21

The hospital says it does not know what happened

She checked herself into a hospital weeks ago for a bladder infection. But nobody could have predicted it would end like this.

When Lynne Spalding went missing from San Francisco General Hospital, her friends frantically searched and left messages on a Facebook page to keep each other hopeful.

, also known as Lynne Ford. On Tuesday, the messages on the "Find Lynne" Facebook page turned from hope to anger. A body was found in an exterior stairwell of the hospital, and the San Francisco medical examiner confirmed Thursday that it is Spaldingalso known as Lynne Ford.

How could this be? Spalding's friends had searched throughout San Francisco, in alleys and shelters, handing out hundreds of fliers. They wondered whether the woman, dazed by powerful medication, was wandering around somewhere.

"So we have a lot of questions as her family and friends," said David Perry, a Spalding family spokesman. "Did anyone see her leave the room? Did she leave alone? Is there videotape of Lynne leaving the hospital or wandering the halls?"

All who looked for Spalding, 57, who has two adult children, assumed the hospital had been searched thoroughly.

"Dumbfounded that they didn't find her for two weeks?! Where the hell were they looking?!" Liz Kennedy wrote on the "Find Lynne" website.

"I honestly believe there should be an investigation into how the hospital areas were not thoroughly checked by the staff," another poster named Sunil Raj wrote.

Hospital officials and police say they are investigating. The hospital says it has no idea how the body ended up in the rarely-used staircase.

"We're distressed," Rachael Kagan, a spokeswoman for San Francisco General Hospital, told CNN affiliate KTVU. "We don't know what happened. That's our top priority, is to find that out."

Spalding was admitted to the hospital on September 19, and her condition was improving when she disappeared two days later, according to the joint statement released by the hospital and sheriff's department.

"She was in fair condition when she left her hospital room shortly after being checked on by a nurse at 10:15 a.m. Fifteen minutes later, the nurse checked on her again, and upon finding her room empty, initiated a search of the hospital," the statement said.

Thirty minutes later after she disappeared, two of her friends and her boyfriend arrived at the hospital to visit, Perry said. They were told that Spalding had been missing for 30 minutes, Perry said.

"Someone has died in a mysterious fashion at San Francisco General Hospital, an institution which is known for healing," Perry said. "And tonight I'm sure the staff of SF General is horrified and confused, certainly the family is horrified and confused."

According to the joint statement, when the patient was not found, the hospital staff notified the family and sheriff's department officials on site. Deputies searched the campus, and did not find her.

Spalding's body was discovered in the stairwell by a member of the hospital's engineering staff who was conducting a routine quarterly check, according to the statement.

"The exterior stairwell is a fire exit that is not routinely used by staff, patients or the public. It is alarmed and locks from the outside; it exits to the hospital grounds at the bottom," it said.