So what if I know that he is not the queen because I know that a third player is? Is there anything I can do?
With calling his bluff, you can prevent him to win two gold but this will ost you one gold. It might be worth it in the endgame, to prevent a win, but you can also hope that another player speaking after you will do it. Position around the table can be critical in the endgame, and a player can end "playing the police" like in poker.