Hmm, yes, once you've established that things are rotten in the state of Denmark, an additional screen switch fixes the problem. Still, "slow and deliberate" means examine screen, wait a second, click, "why do I have this excess of cards", ponder, click, switch screens, "wait that wasn't the card I sold at all".
Entirely avoidable, perhaps, but that's not the point. It's a bug, and therefore it needs to be fixed. I can't imagine someone forced to find out the hard way that they just sold a rare card would be much assuaged by knowing that they were in "Don't do that then" territory.