There is a famous story about a superb Chicago player in the early 1940s who was playing against experts in a national event. There were at least 50 kibitzers at the table. The expert heard his opponents bid easily to a small slam in spades. He sat to declarer’s left and held:
Q2 
5432 
97642 
A7
After tabling the club ace on opening lead, he continued with his second club, won by declarer. At this point, the Chicagoan apologized and said to all that nature compelled him to take a trip to the washroom. Turning to the nearest spectator, he said sweetly:
«Would you please play the rest of the hand for me? Just follow suit.» And he went away.
Declarer naturally reasoned that if his opponent had no further interest in the hand, the queen of trumps must lie on his right. So declarer finessed in trumps though missing only four cards in the suit. The surprised kibitzer won the trick to set the hand.
You won’t find that little ploy in the rule book. But if someone pulled it on me, I might become the reincarnation of D’Artagnan. Anyway, most duplicate fans are far too hooked on a mentally rewarding, challenging game to worry about such isolated instances. Like the others, I have only one thing to say — deal!