He says some memories have since been slowly trickling back, including slight recollections of living in China and Europe. But Lighthart still doesn't know who he is, and is frightened over whether he will ever be reconciled with the man people say he is.
"The crux of the matter of who I really am isn't there yet," he said in an often-emotional interview with The Associated Press on Monday. "And I'm not sure that it's going to come back. This is one of the frightening things."
Police say the 53-year-old man emerged from Discovery Park in Seattle early on July 30 knowing he didn't live in the Seattle area, but unsure of everything else. He flagged down a bus driver, who called police for help.
Officers said the neatly dressed man had $600 hidden in his sock. He says he still has no idea how he got to Seattle, only recalling several peaceful days in the park spent gazing at the trees and sky.
He spent nearly a month at Swedish Medical Center, where doctors told him he has a rare form of dissociative amnesia. After The Seattle Times published an article about him Aug. 20, friends and relatives who saw the story identified him as Lighthart, easily recognizable by his distinctive handlebar mustache.
Seattle Detective Tina Drain of the police missing persons unit said an estranged sister of Lighthart provided an expired American passport and driver's license, Social Security card and other identification that have since been given to Lighthart.
The investigation has left "no doubt" that the mystery man is Lighthart, Drain said.
But that hasn't sunk in yet for Lighthart.
Since his discharge from the hospital Aug. 24, he says he has been receiving counseling through Harborview Medical Center and living in a respite home. That temporary housing ends this week, he said, and although he is looking at another possible residence, he doesn't know where he will stay after that.
"I'll probably be going back to Discovery Park," he said. "I've talked to the social worker at Harborview and the only thing she's suggesting is a shelter and I said that I am terrified of the idea, I am terrified of being assaulted."
Harborview spokeswoman Susan Gregg-Hanson said Lighthart is continuing to receive outpatient care at the hospital and that it is working with him to find a solution for housing. She declined to comment further, citing federal privacy laws.
Neatly dressed in the same blue blazer and khaki pants in which he was found, he spoke at length of the frustration, panic attacks, an overwhelming feeling of being perpetually lost, and fear of again losing the few connections he's made.
"I'm living in this state of confusion because I've got this knowledge, but where has it been used, where is it going to be used, and am I going to be able to retain it?" he said.
Lighthart's history shows a man who worked as an international business consultant after advanced education at a number of U.S. schools and who lived in Paris, Vienna, Sydney, Shanghai and Slovakia.
He readily acknowledges this makes sense; he's fluent in French and German, and has memory fragments of living in Shanghai, Paris and Vienna.
But that life "feels superficial" he says, and something within him resists wanting to be Lighthart. He doesn't recognize the name, and for reasons he doesn't know, he says it brings up "this sense of failure and rejection." He prefers to go by John Doe and not Lighthart.
He thinks the negativity surrounding the name might stem from his guilt over a brief marriage that ended in 1985 when his wife died of a miscarriage and he discovered her body in their Chicago apartment. The civil marriage was never officially registered, he said, and was hidden from friends and family.
That vivid, troubling memory was one of the first that returned, and he suspects he may have started having other brief episodes of amnesia shortly after her death.
Lighthart grew up in Tucson, Arizona, but he says he has few memories of that, other than an unhappy childhood with an alcoholic father and a mother who used prescription painkillers. But he says he doesn't recognize his parents' names and has no recollection of an estranged sister in Las Vegas who contacted The Times.
Drain said the sister told her that Lighthart had stayed with her for a year and a half before she asked him in May to leave because he wasn't working or paying rent. The sister said Lighthart disappeared in late July, leaving his belongings behind.
A message left with the sister through Drain to contact the AP was not immediately returned.
Records show Lighthart was in Calgary in December 2007, but was told to leave Canada four months later after officials contended he was trying to abuse the social system to obtain food and lodging. He said he has no memory of that, but denied he is trying to scam the system here.
"I understand there are detractors and it's something that needs to be said, but definitely no," he said. "This is not fun."
He has been reluctant to contact people who say they know Lighthart. He cites many reasons difficulty getting numbers, not knowing them or whom he can trust.
"I think in most cases it's been that I don't recognize them," he said. "It's just been fear of the unknown."