Question: What happens when a player calls a discard but, picks up the wrong tile and adds it to the exposure? Can he put the wrong tile back on the table and take the correct one?

Answer: It is every player’s responsibility to verify they’ve made a correct exposure. If a player calls a tile for exposure and picks up the wrong tile and it is noticed by another player, the hand should be declared dead. This ruling is not found in Mah Jongg Made Easy.

Source: Although this rule was cited in the 2012 National League Bulletin it was also affirmed in a phone call to the League.