Okay, so this has been bugging me for a while now. But right now "Seer's Passbook" is out on the OCG ( http://yugioh.wikia.com/wiki/Seer%27s_Passbook ) which can banish the top 3 cards of your Deck face-down, and then 3 turns later get them back. My issue is with its interaction with "Pot of Desires". Which banishes 10 cards from the Deck face-down as a cost.
So somebody can activate Seer's Passbook, then later use Pot of Desires, banish 10 cards with it, and then once Seer's Passbook says it is time to return the cards to your Hand that you banished this way, that player can just take 3 cards that are banished by Pot of Desires instead, and you as the opponent would never have a clue that this is happening.
I feel this needs to be fixed before it can be abused too much. Maybe give all cards that are banished a number, and you get to see in the log which number has been moved?
https://www.duelingbook.com/replay?id=19309-4182080
^ replay when we were testing this.
https://www.duelingbook.com/replay?id=1191-4182080
^ same replay, except now my side.