Do you have a fender tag or broadcast sheet for the car. If so the number above the VIN number on the fender tag is the Vehicle Order number this number is also on the Broadcast Sheet. This is the number or paper work the Dealer used to order your Vehicle. If you can find another Vehicle with a VON close to your Vehicle and they know the Dealership then there is a real good chance your car was ordered off the same pad of VONs from the same Dealership. If not you will have to do leg work and contact previous owners back to the person that bought the car off the Dealership. Many registers might have information to help you out if they have enough vehicles in their files.