This is a valid win, due to how the deck gets shuffled ghosts could be after the 3 exits required to win. I was hoping to have time to implement local multiplayer which would prevent this win by spreading the exits between multiple players. Other solutions to prevent it would have been adding more cards that cause you to discard cards on draw (with the lacking animations it didn't feel fair to the player to discard the cards highly often), or rigging the deck to ensure Ghosts enter the field before any exit is found.
Also, with how quickly ghosts can take their turn you may have not noticed they did...