i think he probably buries it and hopes that no one finds out beyond the necessary people, because he loves making up stories for why he is the way he is, and they're always total bullshit. it isn't that he's hiding from the truth, but he doesn't want anyone to feel sorry for him, so he just puts it all on himself, like it happened because he was being a dumbass and racing in a narrow canyon or survived a mammoth shark attack but got pretty chewed up in the process! whether sam knows the truth since he can access all those files is totally up to you. it could be interesting if he knows but charlie doesn't know he knows!