It's been a year since California mother-of-two Sherri Papini seemed to vanish — without a trace — while going for a jog near her home

4 Burning Questions PEOPLE Has in the Bizarre Abduction Case of Sherri Papini

Editor’s note: This story was originally published on Nov. 2, 2017.

It’s been a year since California mother-of-two Sherri Papini seemed to vanish — without a trace — while going for a jog near her home in Redding on Nov. 2, 2016.

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Twenty-two days after she suddenly disappeared, she was just as suddenly found alive on the side of a rural road in Yolo County, California, about 150 miles south of Redding.

According to authorities and her family, her body was emaciated, shackled, bruised and branded. She weighed just 87 lbs.

For months the mystery of what really happened to Papini perplexed both law enforcement and the public. But as the one-year anniversary approached, investigators released several previously undisclosed details about what they have learned while probing her disappearance and searching for those responsible. Among the new information were suspect sketches and DNA evidence.

Despite this progress, mysteries remain. Here are four of the burning questions — and some answers — about the case.

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Image zoom Sherri Papini (right) with her husband, Keith ABC

1. Why Would Papini Have Been Taken and Released?

Law enforcement is still uncertain what led to Papini’s abduction, where she was held for three weeks and why she was set free without an explanation.

“Why was she released?” Shasta County, California, Sheriff’s Sgt. Brian Jackson tells PEOPLE. “It is hard to keep somebody in captivity for 22 days. Why would somebody go to that length? Those are all types of questions we all have.”

In the course of their investigation, Shasta County authorities have received more than 600 tips, traveled across the country, interviewed hundreds of people, scoured surveillance videos and served 20 search warrants.

Some experts have suggested sex-trafficking as the motive, but Jackson says it seems unlikely.

“Just on the facts that we know, it doesn’t seem to be a sex trafficking or a sexual abduction in nature, and that is what we are trying to figure out: What was the purpose?” he says.

Joe Giacalone, a retired New York City police sergeant and professor at John Jay College of Criminal Justice, agrees with Jackson and says sex traffickers would never have released Papini.

“You had her,” he tells PEOPLE. “You had her chained up. What threat was she to you? You have total control. Your operation would be at risk letting her go. These guys are professionals. She is going to be able to identify you. How do you not know that won’t happen?”

However, says Giacalone, the abductors could have been amateurs “and that is the reason it ended like this.”

Image zoom Keith and Sherri Papini with their two children (center)

2. Why Was There No Ransom Request?

Though a $50,000 reward was offered by local officials and Papini’s family and an anonymous donor offered a separate, undisclosed amount for her safe return, the money went unclaimed.

“I think that is what is really perplexing the police,” Giacalone says.

“There is no rhyme or reason for [the kidnappers] never making a request for money,” he says.

3. Why Did It Take This Long to Produce Suspect Sketches?

Though investigators worked closely with Papini from the start, they say it took time for her to come to a place in her recovery to work with a sketch artist. The sketches also had to be approved by the FBI before their eventual release.

At the Woodland Memorial Hospital in California after she was found, Papini gave Shasta County sheriff’s investigators a “limited description” of the two women she said were her captors.

But, the sheriff’s office said, her abductors had “made efforts to conceal their identities with face coverings” and “Sherri would also “keep her head down when in their presence to avoid being battered by them.”

Once the sketches were complete, authorities reviewed them again with Papini and “compared the sketches with known witnesses or contacts identified during the investigation to see if the sketches matched any known parties.”

No matches were found, they said.

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Image zoom Sketches of the suspected abductors in Sherri Papini’s disappearance FBI

Image zoom From left: Keith and Sherri Papini Courtesy Keith Papini

4. Will DNA Solve the Case?

Last week, authorities said Papini had both male and female DNA on her when she discovered last year.

“The male DNA was compiled from the clothing Sherri was found wearing,” Sgt Jackson says. The female DNA sample was taken from her body at the hospital, he says.

The samples were uploaded into the national CODIS DNA database in April or May, according to Jackson, but there have thus far been no matches to known offenders.

The DNA from Papini’s husband, Keith, was not among the two profiles, authorities said.

Jackson says Papini’s alleged female abductors gave her clothing to wear, so it was possible “that the clothing that was provided to Sherri are clothes that belonged to somebody who was an acquaintance of the captors — and hopefully down the road, once we get these females identified, we will get the answers for that.”