Were you playing against Half-Bloods?
On their slot wheels, the upped and unupped versions of the same card can appear at the same time during the spins. You only win the card if you spin 3 of the same version of the card (either 3 upped, or 3 unupped). You can tell from the bottom left of the reel, since upped cards have a small white triangle on them. Anything else, and you don't get the card.
