Yes, that does it. It draws a card from your deck but it is invisible and you can't recover the lost card. You discard your hand down to seven cards but because you had drawn an invisible card, you ended your turn with eight cards in hand. so next turn when you ended your turn, you had to discard a card, and the invisible card was shown as an outline. It's an awful bug, but is easily prevented if you pay attention to your hand size before you draw.