Originally Posted by EpicSchwinn

this.
If it has a flip flop hub, tracking him down might not be worth it. He probably won't return your calls anyway. Just put a cog and lockring on the other side of the hub and call it good if the rest of the bike is ok.

EDIT:
Looks like you have a quick release back wheel. In other words, you're gonna need even more parts to make it a proper FG. Find this man and make him pay.