Happy Accident (HTTYD-RotG crossover/hijack) (UNFINISHED)

Three years ago, my friend Jack Frost got trapped under ice and drowned. But recently he's been back. Not alive, but he says he's not a ghost either. He has white hair now and can float, plus he acts the same, but I'm the only one who can see him. Something to do with believing...? Anyways, the problem is, he doesn't remember anything. He thinks he was born in the pond that killed him. I don't know if I should tell about his sister, or that I knew him. I probably would, but his family moved after his death. If he goes looking for them, I might never see him again, and I couldn't handle that again.