Just to clarify, in the US at least, the lender can not keep the “profit” from the sale of your car (or home for that matter). They can keep the entire unpaid balance of the loan, plus any associated fees and expenses (late fees, attorney fees, repo costs, etc.). They must give you any remainder. If they can’t locate the owner the funds are held and escheated according to state law. If the amount of the sale does not cover the entire amount due then you are still on the hook for that even though you don’t have the car any longer. And if they write that amount off you will be taxed on it as income. Ouch.
ETA - the lender is supposed to keep a detailed record of the fees and expenses incurred. If they can’t provide you with that you may (repeat: may) be able to avoid that part of the bill.