why my friend disappeared in facebook?

[Rachel]

He either deactivated/deleted his facebook, or he unfriended/blocked you. Facebook will not notify you when you are unfriended. If he unfriended you, you would still be able to look up his profile and interact with him, but some things might be set to private. If he blocked you, you won't even see his name in the search bar and you will not be able to interact with him. However, if he deleted his facebook it would be the same as if he blocked you. You would not see his name in the search bar and you would not be able to interact. It would be as if the profile never existed.

A way to find out is to ask a mutual friend if they can view his profile. If the profile is viewable from another friends account, then you were blocked. If it isn't viewable to them anymore either, then the profile was probably deleted unless he blocked both of you. You can also make another facebook account and see if you can view his profile from there. Only your individual account would have been blocked if he blocked you. You could also go the easy route and just ask him what happened.