Holy moly that sucks. Aren't there partial stampings of the vin stamped on various areas of the car? If by some miracle, you find it, you should have enough to legally get it back. It's yours and it belongs on your car, those numbers, and your documentation will tell a story. The fact that someone unwittingly, or wittingly, purchased it is irrelevant.
Of course, have you considered that you were told a story? Not saying anything one way or the other, but I'd hate to put a tone of effort into a search only to find out I was duped into a bad trade.
best of luck brother