Russell Knox is a Scottish professional golfer who almost suffered an embarrassing penalty when he accidentally dropped his club in a greenside bunker as he was assessing his stroke. His sand iron slipped out of his hand, falling into the sand, just missing his ball.
You may think that Knox incurred a penalty under Rule 13-4b, which states that; The player must not touch the ground in the hazard or water in the water hazard with his hand or a club. However, perhaps surprisingly, part of Exception 1 to Rule 13-4 states; Provided nothing is done that constitutes testing the condition of the hazard or improves the lie of the ball, there is no penalty if the player (b) places his clubs in a hazard. In this instance of the Rules, accidentally dropping a club is the same as placing a club. Of course, if Knox’s club had caused his ball to move as it fell into the bunker, he would have incurred a penalty of one stroke, the same penalty as causing your ball to move anywhere else on the course. The ball would then have had to be replaced where it lay in the sand, to avoid the penalty increasing to two strokes in stroke play or loss of hole in match play, for playing from the wrong place.