Kiersten Carlin combed the streets of Downey last week after learning that her dad, Larry Everett Starks, had been spotted there.
He was released from a hospital without anyone realizing he was a missing person.
The veteran and former San Diego sheriff's deputy disappeared in Florida four years ago after going off his medication for schizophrenia.
On Saturday, Carlin learned that he was back in the hospital in Long Beach.
"I run into the emergency room and there's my dad, and it was the happiest moment of my life," she said. "I talked to him and he recognized me and I told him that I was taking him home and I was going to take care of him and he didn't have to worry about any of this anymore."
Starks will remain in the hospital for treatment for a few more days.