There could be a purchase money security interest if the seller financed the transaction; but we're not going to solve this conundrum by guessing. I suggest seeking clarification from your bankruptcy lawyer.
True. Here, though, the lien would have had to be acknowledged in the original bankruptcy filing, or it would have had to be asserted by the creditor during the bankruptcy proceeding. I'm assuming the former, because if the creditor challenged discharge it is difficult to believe that the creditor would later neglect to recover the property. While other possibilities exist, I suspect that llworking is correct in her inference that the ATV is a titled vehicle.