I'm not surprised to hear that the folks at DMV were unable to get you the information. I suggest that you read the following thread...
http://www.specialservicemustang.net...ead.php?t=2676
...and follow the instructions to get the form to request the Registration History on your car's VIN. The people at the coutner probably do not know the procedure to get that information.
Good luck, and let us know how you make out.