If you've ever been to a professional golf tournament before, you know there's one rule that absolutely must be followed: don't pick up a ball — even if it happens to belong to Tiger Woods. Seriously, don't do it.

We've seen fans attempt to take home a priceless souvenir before, including a lady who was shoved by a guy in the crowd as she tried to reach down and pocket Charl Schwartzel's ball at Doral in 2010. It was the most memorable fan-trying-to-pocket-a-ball moment in recent memory ... until a kid at the John Deere Classic usurped her during the final round.

With the tournament hanging in the balance, Troy Matteson stepped onto the tee on the par-4 18th hole -- just moments after he canned an incredible 59-footer for eagle on the par-5 17th -- and hit a wayward drive into the trees.

[Related:Zach Johnson wins the John Deere Classic on second playoff hole]

The ball landed near a young boy who tried to pull a fast one on some unassuming gallery members by running over and picking up the ball. There was just one problem: Matteson needed the ball to finish his round. A couple of fans in the crowd saw the entire situation and called the youngster out.

Busted. Based on the footage, it looks like the kid knew he was in the wrong after he tried to hide the ball in his hand. You'd think someone would have informed him that you never pick up a ball during a tournament, but when you're caught up in the moment of potentially walking home with a sweet souvenir, the rules go out the window.

Thankfully, the kid's poor decision didn't cost Matteson the tournament — at least not on the final hole of regulation. He was able to drop the ball nearest the spot where it landed and managed to get up-and-down to force a playoff that he eventually lost on the second hole.

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