Playing the Ball as It Lies (Rules 8 and 9)

Rule 9.2: If it is known or virtually certain that a player, opponent, or outside influence moved a ball at rest, the ball must be replaced to its original spot. If the original spot is not known, the ball must be replaced on the estimated original spot (Rule 14.2).

Source: Rule 8.1, Rule 13.1, Rule 9.2, Rule 14.2

Send this to your friend — argument over.