[ewill3rd]

These are not times to be playing games with things that might affect your credit rating.
Paid of loan or not, mistake or not, if this goes to your credit your score will be in the tank and trying to get a decent loan at a decent rate with the changes taking place in the lending industry is financial suicide.
Your attempt to "show them" is going to backfire in the worst of ways.
If I read this right (and I may not be) you may even face criminal charges for hiding the vehicle, for whatever your reasons are.
I'd agree with the overall consensus of this topic, no reason to stop paying, as frustrating as it may have been you should have gathered your documentation and done some certified mail or sat on the phone for 5 or 6 hours to get it straightened out. Their mistake or not you are now in a breach of contract situation and possibly a grand theft auto situation.

I hope it all works itself out.