Honestly, here's a completely non-legal answer that will probably serve you best. Consider it a learning experience that cost you $650, be done with it, be done with your friend and NEVER loan friends or family money again (However, I am curious as to why you thought this guy was a good risk to begin with. If they can't get a loan from a bank or a credit card, why would you loan them money?).
If you have the extra money for friends/family and you want to help them, give it to them... DON'T LOAN IT. Loaning money causes nothing but problems for the person loaning it and does nothing but strain relationships. It's simply not worth it.
Chalk it up as a loss and move on.