Just to throw a little fuel on the fire....
Upon finding an extra club in your bag, are you required to remove it? Since the penelty is based on a maximum of 2 holes lost in match play, what's the difference if he carried it for 18 holes? If it was noticed on the 18th, the penelty would be the same.
I wonder what would happen if a player used the club identified as the 15th during the round? How would an opponent ascertain that some other club had gone unused, thus the player had kept to the actual usage of no more than 14 clubs.
Damn... I should go start a fight somewhere... I'm good at all the questions and none of the answers.