[The Chief (tm)]

OP,

Love the original sticker; at the very least you should make a poster of it and hang in the garage.

I might guess that if this was a (much) newer car, you could have a shot at running the VIN through Carfax, et. al., to maybe get a handle on the paper trail of buyers & sellers. But who knows if it would turn up *now*, especially since (and of course I hate to say) it is quite likely that the car is sitting in a barn or simply hasn't been on the road in ages, hence no recent DMV transactions.

(Still, maybe some sort of records request in the last state that you know it was registered in?)

I think that the gang here would be very interested in any updates in your search, if for no other reason than the methodology. And if you somehow manage to find the thing, awesome! Good luck for sure.