Final answer:
In golf, if a player’s ball is moved out of bounds and thrown back onto the course by someone else, and this is discovered after a stroke is played, the player must place a ball where it was originally at rest out of bounds. The player incurs a two-stroke penalty and the stroke from the wrong place counts. If not corrected before the next hole starts, the player is disqualified.
Step-by-step explanation:
In match play golf, if a player's ball is moved out of bounds by an external influence and then thrown back onto the course where the player subsequently plays it, the proper ruling depends on whether the player knew or should have known that the ball was played from a wrong place.
In the scenario given, where the player's caddie informs them after the stroke that the ball at rest had been moved by an outside agency (someone picking it up and throwing it back in bounds), the correct procedure is for the player to correct the mistake by placing a ball on the estimated spot where the original ball had come to rest out of bounds.
The stroke made from the wrong place does count, and the player incurs two penalty strokes according to The Rules of Golf. If this procedure is not followed before the start of the next hole, the player is disqualified.