The owner of the note may have the right to possess the car (depending on the terms of your agreement with them), so there is little chance you have a claim to keep the vehicle if they attempt to repossess it. Proving a fraud under these kind of circumstances is a hard case for the State so they typically leave the matter up to the parties to settle in the civil courts. However, Houston cops are no strangers to aggressive tactics, so it wouldn't surprise me if they had decided to start prosecuting people who are behind on payments.
I would recommend calling a local criminal defense attorney. They may be able to tell you whether or law enforcement agencies in Harris County are engaging in these sort of tactics.