Dr. Merritt Ayad told the Seattle Times police found Lighthart in the street. He had a passport and some old identification from Europe but said he had no memory of who he is.
He is now in a state hospital in Las Vegas.
"When we get someone like this we have to see if there's any way we can trigger memories," Ayad said. "We can't let him wander around here. We're still left with what to do with him. Part of him is willing to accept this is who he is, but he doesn't remember much."
Lighthart surfaced in Seattle in July. He was identified when a former student in Shanghai, where Lighthart had taught English, recognized a picture published on the Internet.
He had been living with a sister in Las Vegas, Nev., who said she told him to leave because he had not been paying her rent. The sister, who did not want her name used, said he might have been looking for her in Las Vegas, N.M.