Two things really quick from league.
The Palantir of Orthanic only lists the first card you put back from someones.
The other problem I have had is when someone knows they will lose a game and they leave the game, either by closing their browser or something and you are stuck there for the ten minutes it takes.
I lost a game in round 4 because of this, I thought it had been 10 minutes and I closed my computer down and it gave me the loss, it sucks, it was my first loss of round 4 and when I got on the next day and checked it said I had a loss and I was pissed.
I hate that your opponent can screw you out of over ten minutes of your time.