Retraction of card played
West leads Club Q.
Dummy has A x and South, Declarer, has K 10 x. West immaterial.
Declarer calls for the 'Ace' and at his turn plays the King. Immediately 'oops, that was not what I was going to play'. Director please.
Declarer maintains that this was a slip of the finger and asks to be allowed to replace the King with the small card. He argues that it is similar to an unintended designation of card to be played from dummy, which is allowed to be changed.
Law 47 does not allow retraction of card played from hand even if it was (obviously) unintended. Therefore he cannot replace the played card.