I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear about your situation.
If he's refusing to return the car, did not pay for it, and is not communicating with you regarding when he's planning to return the vehicle, then it's legally been stolen. His permission to take the car expired at the minute he decided he wasn't going to bring it back as the two of you agreed. So you could file a police report.
In addition, if you know where this person lives, you have the ability to go to the house and take the car back with your key, since it's your car. Or you could ask a tow company to come and take the car back. You can knock on the door and ask for your key back and if he doesn't return it, let him know you'll be suing him in Small Claims court for the cost of getting a new key made (plus your filing fees). It's also possible to call the police and request a civil standby, asking that they go to the house with you to pick up the car, to make sure there isn't any problem.
If you'd prefer not to get the police or courts involved, you have the option of sending a letter, via certified AND regular mail, giving him the option to return the car by a date you specify or be sued for the full value plus punitive damages. Or you could leave a message that says as much, since letters take a few days. The only problem is, you might not want to wait a week for him to get a letter, and people tend to take certified mail more seriously than a phone call.
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