That's a tough one. Do you have a written receipt for the transaction? What VIN is printed on that? I'm not sure if you can get the law involved on this deal. You may have to sue him or find a way to put a lein on the car. I would take the VIN of the car to the DMV and ask what the registered owner is in case its not this kid you bought it from. If its not his, it may be a legal matter then.