I have to be honest... I'm surprised no one mentioned the money involved in hiring a PI. You're a college student, can you really have that much money just lying around? They're not cheap.

I also agree that it's probably not a good idea simply because it sounds like he doesn't want to be found. Now, I see nothing wrong with getting in touch with co-workers from the grocery store and seeing if they know anything about him, or even if he still works there.

Try not to be curious too much. If he wanted to be in touch with you, he would. You never know, in a couple of months, he might realize you were right and that maybe he's better off for it, and will get in touch with you then. Or maybe right now he just wants his privacy while he continues to recover.