Aside from taking legal action to enforce your claim, I am not sure what else you can do. Consider the cost involved vs. the amount left owed on the other loan.
Consider also that even though you accidently released the title to the car, you should still be able to enforce the unpaid obligation through a default judgement if it should come to that.
If you can find out who the other bank is, you might consider contacting the other bank to let them know the disputed status of the title.
Finally, you should review the procedures in your Note Department to make sure collateral that is cross pledged is properly marked both on your computer system, and on the physical evidence of the collateral.
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I am not a lawyer and I don’t play one on TV. These are simply my own opinions.