“If the loan is null and void, that means it’s no longer a legally binding document. Because of that, you technically don’t own the car anymore. As a result, you’ll have to take it back to the dealership.
However, you should get your down payment (if any) returned and credit for the value of your trade-in. Unfortunately, you’ll be without a car for a while. It’s in your best interest to find out why the loan fell through and what you can do to secure financing.
In the future, make sure to get pre-approval before you go car shopping. This is a rare instance where the dealer let you drive away before approving you for financing. Be wary of such dealers in the future and go to a bank or credit union for financing.”