Those kinds of stories are always fun, but the reality is all the LARGE fonts were already hearts. It would have been quite a coincidence for a new owner to all of a sudden change to a spade on the very first order of SMALL fonts ...just to decide they were bad luck.
The story I heard was the casino had ordered spades but didn't like the way they looked so changed the next order to the present hearts. For the same reasoning mentioned above, that doesn't make sense either.
So it looks like the SPADES are just what they are...an error.