Well you already made the stolen car report and no matter what you owe him he cannot hold your car. He would have to go after you civilly for the money owed, if any, but it sounds like he owes you. Due to the circumstances you need to take your stolen vehicle report, go to the prosecutors office and file the theft of vehicle or receiving stolen property on him. When its a car its a felony and if the prosecutor seems to think it fits they will issue a warrant out for his arrest. There are certain things that keep an issue like this in the civil arena, however, it sounds more like a criminal issue for you. Hopefully your car is enter into LEADS as stolen. Try this first.