What happened to Chelsea Cobo? Young mom vanishes without a trace as shadowy witness implies foul play

The mother of a missing Brooklyn woman whose unsolved 2016 disappearance has prompted suspicions of trafficking and foul play is poised to launch a networking app that she hopes can spare other families from the trauma she's endured over the past eight years.

Chelsea Cobo was 22 when she was last seen in Sunset Park on May 6, 2016. She had a 10-month-old son but had recently been hanging out with a sketchy new crowd, a group she met during a dubious hospital stay months earlier, according to her adoptive mother, Rose Cobo.

Rose Cobo, who raised her adoptive daughter since she was just over a year old, told Fox News Digital the new group struck her as suspicious. She said the group introduced the young mother to serious drugs. Recognizing a problem, Chelsea checked into rehab, she said. Then she checked out and never came home.

Police and prosecutors interviewed numerous witnesses, conducted searches and scoured through surveillance videos, but the case remains unsolved.

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Rose Cobo said she suspected her daughter had been trafficked or worse. The day after she last spoke with Chelsea, a strange man from the hospital, who her daughter had only recently begun seeing, left her an ominous voicemail, claiming to have dropped Chelsea off and that he had "nothing to do" with anything else that might happen.

She told Fox News Digital this week that just discussing the harrowing conversation makes her uncomfortable.

"I'll never get used to it," she said. "It just knocks me out. It took the wind out of me."

"I'll never get used to it. It just knocks me out. It took the wind out of me."

— Rose Cobo

Over the years, the adoptive mother has pushed for answers, raised awareness and even interviewed witnesses on her own, sharing her findings on social media and with reporters. Now she's hoping that experience, and the new app called 911Missing, which she is pushing with the families of other missing people, can help provide answers in her daughter's case and to other families.

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"I believe maybe somebody someday will pick it up and put the pieces together and maybe figure out how Chelsea went missing," Rose Cobo told Fox News Digital.

One persistent problem she's faced, she said, is detectives on the case have kept her in the dark about what's going on. So at one point, she went to speak with one of the witnesses herself, confronting a man who lives at the house where her daughter was last seen.

In audio of the conversation first aired on the ABC and Hulu documentary "Missing: Chelsea Michelle Cobo," Rose Cobo knocked on the door at the townhouse and bluntly asked a man inside if her daughter was alive or dead.

"I been telling the police," the unseen man replied. "Police know she’s gone. How come you don’t know she’s gone?"

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"She's gone?" Rose Cobo replied, the shock in her voice apparent. "She's gone?"

The NYPD declined to comment on the witness's claim.

A screening of the documentary brought many people to tears in an audience at the East Hampton Library during the Hampton's Whodunit conference in East Hampton, New York, this month. One woman left with her face hidden behind her fingers. A friend placed her hand on Cobo's back.

During a panel discussion afterward, Rose Cobo took issue with secrecy surrounding the case and lamented that more people in the Sunset Park neighborhood, where her daughter was last seen, may not have been asked to check their surveillance cameras for evidence in the case.

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That's where she hopes the app will help by rapidly connecting businesses and homeowners, amateur web sleuths, investigators and other citizens with information about a disappearance.

"It's not only where you are, it will travel with you," she said "Hypothetically, you're going to Colorado. You're there, and you just want to get what's happening in the neighborhood. You could set it in a mile radius, a five-mile radius, a 250-mile radius."