I don't have the exact hands, but have all relevant facts from this ruling in a local league. West led the queen of clubs against 3NT by South (I don't have the auction). Declarer won and ran the queen of spades, West winning and switching to a heart. East played the jack, and South ducked. East continued hearts to West's queen while South ducked, and West played the nine of hearts which South won, dummy pitching a club. Declarer now played a diamond to the king, cashed the spades, and then finessed the jack of diamonds. At this point, for some reason, East conceded the remainder, and South closed his hand, but West asked "Who has the master heart." and East responded "I do." West said "it is one off then," but declarer objected, saying "only if you play a heart".
How do you rule? Is it a UI case, or is the K♥ a major penalty card as it was "named" by East when he said "I do"?