School's out

This is a textbook deal that was flubbed at the club last night (hands rotated and low cards are approximate):

                ♠ A 2
                ♥ K J 7 5
                ♦ K 9 3 2
                ♣ 10 8 5
===
                ♠ 10 9 4
                ♥ A Q 10 8 4
                ♦ A J
                ♣ A 4 3

After two passes South opened 1♥. North bid 2♣ Drury showing a heart fit and limit raise values. South rebid 4♥, ending the auction.

West led the 3♥. Declarer played two rounds, both opponents following, then played the ♠A and another. East won to shift to a club, knocking out South's ace.

Declarer now played the ♦A and then the ♦J to the king to lead a third round, ruffed in her hand. She was hoping for ♦Q 10 x in either defender's hand. The ♦9 would then be good for a club discard. That didn't work and she made four for a score of 620 and 1 matchpoint on a 7 top.

Here are all four hands:

                ♠ A 2
                ♥ K J 7 5
                ♦ K 9 3 2
                ♣ 10 8 5
♠ K 6 3                       ♠ Q J 8 7 5
♥ 6 3                         ♥ 9 2
♦ 10 8 7 6                    ♦ Q 5 4
♣ K J 9 2                     ♣ Q 7 6
                ♠ 10 9 4
                ♥ A Q 10 8 4
                ♦ A J
                ♣ A 4 3

Do you see where declarer went wrong? After drawing two rounds of trumps, she should lead a diamond from dummy and play the ♦J. If it wins, she can unblock and the ♦K is available for a club discard. If the diamond finesse loses, she is no worse off. She can still discard a club on the ♦K and four still makes. It's a no-cost play.

This player did't see the textbook play. She is already on summer break -- I'm just sayin'.

Here's the same deal with BBO's Handviewer: