The explanation I got was somewhat confused, but as far as I could understand, the game is out of print, only a limited number of copies (or maybe even only the one?) were shipped to the con, and the one which should have been earmarked for the games room got into the "to sell" pile instead. They didn't realize anything was wrong until they were going through their list of game sessions to schedule/prepare and found that box missing. And I guess by then all the sale copies in the dealers' room were gone.

Anyway, I agree, it worked out just as well in the end.