Thanks for reporting that problem.
I think there are 2 problems at hand, which may (or may not) be interconnected.
1) You couldn't continue with the game.
2) The game was somehow ended and recorded as a loss for you.
I can't help you with 2), unfortunately.
1) seems to be the case of an obtuse interface. What happened is that when you had played your 2 Horn of Plenty, the game still couldn't automatically advance to your Cleanup phase because you had 1 coin token that you could legally (though pointlessly) convert to a coin to be used for this turn (might have even been useful if the Banquet event had been present).
For reasons I don't know (though I strongly suspect that this being a Mission turn is connected to it), the game interface didn't show the "End Turn" button, which is usually used to advance from the Buy phase to the Cleanup phase. What you have to do in this case is to use the slider for the coin token conversion und move it to the left, so "0 Token" is shown on the button (see attached picture). If you then press the button, the game will continue.