My question is, why did the "friends" leave so early instead of staying behind to help find him? Unless they knew what happened to him or they're hiding something...
I believe him and a couple of his friends had taken LSD and he probably overdosed. The friends didn't want to get in trouble for taking it too so they hid the body and threw away his clothes to make it seem like something mysterious had happened. All of his "friends" left PCB awfully fast.