If your contract includes the right to repossess the vehicle, and you registered your lien with the DMV, then you can repossess the vehicle, but not until the bankruptcy court has lifted the automatic stay against you concerning the vehicle.
If you are simply an unsecured creditor, then you have no rights to the vehicl at all, and your option is simply to stand in line with all of the debtor's other unsecured creditors.
If the vehicle was expensive, you may want to contact a local bankruptcy lawyer to provide you with info concerning the cost of trying to recover the vehicle or its value.
Alternatively, if you are a secured creditor, and this is a Chapter 7 bankruptcy, then you can simply wait until the debtor receives the discharge judgment and then you can commence repossession.
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