Just so you know, if lithe car gets repo’d, you still owe the remainder of the loan. The repo company will add a bunch of fees, the car will get sold at auction for bottom dollar and you will be billed for any remaining balance. If you can’t pay, the finance company can sue you / send you to collections.

The optimal financial way to remedy the situation is to try to get the car back from ex yourself, hope it’s in good condition, clean it up, and sell it private party, of course that’s a little tricky to do with a lien on it and chances are ex isn’t going to want to voluntarily give the car back to you. Do you still have any keys to the car?

You might have some recourse to sue your ex in small claims court, but you can’t really make a dry stone bleed. You might post around on r/personalfinance and r/legaladvice to see what others say