Rory McIlroy couldn't help but burst into laughter after Shane Lowry forgot to mark his ball and picked it up during the second round of the U.S. Open

The U.S. Open is as much a mental test as it is physical. Still, the rules violation Shane Lowry found himself in Friday afternoon at Oakmont was so absurd that he and Rory McIlroy could only laugh at it.

Shane Lowry and Rory McIlroy found a moment of hilarity amid a deeply disappointing second round for each player at the U.S. Open at Oakmont, with the Irishman receiving a one-shot penalty as a result