A Georgia mother is stepping up efforts to find her missing daughter, Tiffany Michelle Whitton, who vanished last September.
Tiffany Michelle Whitton, 27, was last seen outside a Walmart near her Marietta, Ga., home at 2 a.m. on Sept. 13.
No one has heard from her since, including her 6-year-old daughter.
"I suspected something was wrong when she stopped posting on Facebook," her mother, Lisa Daniels, tells PEOPLE. "We had not been on very good terms at the time but I always kept up with her through Facebook."
Then, when Daniels' birthday passed without a call from her daughter, she got really worried.
"Regardless of the ups and downs in our relationship over the last few years," says Daniels, 49, who lives outside Atlanta, "she has never failed to call me on my birthday."
Daniels, who's caring for her granddaughter, is not the only one who is concerned.
"What really worries us is that she literally vanished without a trace," Officer David Baldwin of the Marietta Police Department tells WXIA-TV Atlanta.
Police are keeping a tight lid on details of the investigation, declining to say who last saw Whitton or what she was doing near the Walmart so late.
Her mother has now started a Facebook page to help find her daughter.
"Since people don't just vanish into thin air, I believe there is at least one person out there who can provide the answers we so desperately need," she says.
"I would like to appeal to that person to come forward and help us bring Tiffany home," she says.