Hmmm... maybe the issue was you were out of mana (the bar next to health) to cast cards? What happened when you tried to click on the yellow squares?
So the card is exhausted but no angel appears, and the yellow squares still highlight the board... Strange. Definitely a bug, and no idea what would cause it. Hopefully it will just be resolved when I recode that part of the game (the current version was rushed to meet a deadline). Thank you for the report!