You can go ahead and look for it, Black to move. On the face of it, it just looks like I played a stupid game against a stronger player, but a combination was the difference between losing and grabbing an advantage. I suspect that neither of us saw, nor would the casual examiner of the game, but it is critical.
Different position; again, Black to move – find the moves. Hint: If you solve position 1, it will make it a lot easier to solve position 2.