Ferryman is in the kingdom, and Gladiator/Fortune is the chosen card for Ferryman. If someone plays a Gladiator and the opponent doesn't reveal the card, Gladiator says to trash a Gladiator from the supply -- Gladiator is not in the supply in this case but one is still trashed if it's on top of the pile, even though by the game rules this should fail. This is a bug right?
Could be. I was under the impression that it got errata like some other cards (e.g. Farmer's Market) to remove the "Supply" part of its text. But looking at the wiki and the rulebooks makes this seem not true. I've asked for clarification, but as written it is a bug, yes.