Depending on the laws in your state and the receipt you got you probably can get your money back. It may take a threat or actual trip to small court. If nothing else you may be able to renegotiate the deal?

The question is did you pay extra for a numbers matching car? Does it matter to you? There is some difference in value but what that $$ is varies quite a bit. Often there are too many apples to oranges to figure it all out exactly. If it isn't a more rare model or you are planning an all original perfect type restoration it may not matter that much. Just think of how many 350 cars are not sporting a 400 or 455. Those are probably considered more desirable and therefore "valuable" but certainly less original.