After Snapchat Messages, Mom Fears Teen Being Held Brianna Herrmann, 15, has been missing since April 29 By Kate Seamons, Newser Staff Posted Jun 16, 2015 8:22 AM CDT 23 comments Comments Brianna Herrmann and her mother. (Facebook) (Newser) – Brianna Herrmann, 15, has been missing since April 29. That was when she reportedly sneaked out of her San Diego home and vanished—though not entirely without a trace. The car she made off in, her mother's, was found abandoned in early May; potential sightings of her in LA and Irvine have been called in. And there's the ominous Snapchat messages. The teen's mother, Rhona Kauffman, tells NBC News via Dateline that Brianna Snapchatted with a friend soon after she went missing, saying she was being held against her will in an LA home. KGTV last month reported that the LAPD swarmed what they believed to be that home on May 12. They found a room matching the description Brianna had given her friend—it held a mattress on the floor—but she was not there. Neither was the man she's believed to be with: Timothy "Dean" Rivera, 19 or 20, who Brianna met on the beach the month she disappeared. NBC News describes him, by way of police, as a possible drug dealer; the family is more blunt. A GoFundMe page set up to raise funds to assist in the search alleges that Rivera "preys on younger vulnerable girls." Kauffman doesn't think her daughter intended to leave for good, noting she left her wallet and retainer at home, and the Help Find Brianna Herrmann Facebook page says that "Information was received that she has been seen possibly being forced to prostitute herself in the El Sereno area of Los Angeles." A $10,000 reward is being offered to anyone who can locate Brianna. In the meantime, "I have to keep fighting," says Kauffman, a lawyer who has put work on hold for nearly two months to search for her girl. "That's what a mother has to do."