During the third round of the 2011 WGC Bridgestone Invitational, Adam Scott’s ball in the fairway was struck and moved by fellow-competitor Ryan Moore’s tee shot. After consulting with an official, Scott lifted his ball, cleaned it and dropped it. Rule 18-5 (Ball at Rest Moved – By Another Ball) says that when a ball at rest is moved by another ball, the ball that was at rest is to be replaced. So, why did Scott have to drop his ball rather than just replace it? In order to replace the ball from where it was moved, the exact location must be known. Since the exact location of Scott’s ball was not known, Rule 20-3c (Placing and Replacing – Spot Not Determinable) states that the previous location must be estimated and the ball dropped as near as possible, but not nearer the hole, to the estimated location. Scott was allowed to clean his ball as Rule 18 is not one of the 3 Rules listed in Rule 21 (Cleaning Ball) where cleaning is prohibited. As for Moore’s ball, Rule 19-5 (Ball in Motion Deflected or Stopped – By Another Ball) requires his ball to played from where it came to rest after the collision.