I've done this a few times, where I changed my mind on what I was going to play for my turn and accidentally had more cards selected than needed. (ie: need two gold to collect gold, I had an additional card still selected) and when I picked up the gold it discarded all three cards even though I only needed two. It would be great if there was a validation procedure to check if there are more cards selected than actually needed.
Yes it is my own fault for having them selected, but it would never happen on a physical version of the game. Online however, it is easy to miss something that was selected and not deselected.
