Golf Ethics Test

You are playing in the state championship tournament and your match is all square after 17 holes. You had the honor and hit your drive two hundred and seventy five yards to the middle of the fairway, leaving a an eight iron to the pin. Your opponent hits his drive deep into the woods to the right of the fairway. You help your opponent look for his ball. Just before the permitted five minute search period ends, your opponent says: "Go ahead and hit your second shot and if I don't find it in time, I'll concede the match."

You hit a great 8 iron about ten feet from the pin. You then hear your opponent yell, "I found it!" followed by the sound of a club striking a ball. You opponents ball lands six inches from the pin. 

Here is the question: 

Do you pull your cheating opponent's ball out of your pocket and confront him or do you keep your mouth shut..??