S.L.
Have you tried Facebook? Look him up on there, see if he has a profile. If his name is unique enough, you can find him without knowing where he is. Or if you have friends in common, you might be able to find him that way.
If you do find an address or email address or other way to contact him, I suggest you just say that you miss him and maybe you're sorry and that's it. I tend to talk too much and put people off in a situation like this. Good luck!