Got the answer to my last question by reading the entirety of rule 18- it seems a drop would be correct.
Ball At Rest Moved
All defined terms are in italics and are listed alphabetically in the Definitions section.
18-1. By Outside Agency
If a ball at rest is moved by an outside agency, there is no penalty and the ball must be replaced.
Note: It is a question of fact whether a ball has been moved by an outside agency. In order to apply this Rule, it must be known or virtually certain that anoutside agency has moved the ball. In the absence of such knowledge or certainty, the player must play the ball as it lies or, if the ball is not found, proceed under Rule 27-1.
(Player’s ball at rest moved by another ball – see Rule 18-5)
18-2. By Player, Partner, Caddie Or Equipment
Except as permitted by the Rules, when a player’s ball is in play, if
(i) the player, his partner or either of their caddies:
• lifts or moves the ball,
• touches it purposely (except with a club in the act of addressing the ball), or
• causes the ball to move, or
(ii) the equipment of the player or his partner causes the ball to move,
the player incurs a penalty of one stroke.
If the ball is moved, it must be replaced, unless the movement of the ball occurs after the player has begun the stroke or the backward movement of the club for the stroke and the stroke is made.
Under the Rules there is no penalty if a player accidentally causes his ball tomove in the following circumstances:
b. Ball Moving After Address
If a player’s ball in play moves after he has addressed it (other than as a result of a stroke), the player is deemed to have moved the ball and incurs a penalty of one stroke.
The ball must be replaced, unless the movement of the ball occurs after the player has begun the stroke or the backward movement of the club for thestroke and the stroke is made.
Exception: If it is known or virtually certain that the player did not cause his ball to move, Rule 18-2b does not apply.
18-3. By Opponent, Caddie Or Equipment In Match Play
a. During Search
If, during search for a player’s ball, an opponent, his caddie or his equipment,moves the ball, touches it or causes it to move, there is no penalty. If the ball is moved, it must be replaced.
b. Other Than During Search
If, other than during search for a player’s ball, an opponent, his caddie or hisequipment, moves the ball, touches it purposely or causes it to move, except as otherwise provided in the Rules, the opponent incurs a penalty of one stroke. If the ball is moved, it must be replaced.
(Playing a wrong ball – see Rule 15-3)
(Ball moved in measuring – see Rule 18-6)
18-4. By Fellow-Competitor, Caddie Or Equipment In Stroke Play
If a fellow-competitor, his caddie or his equipment, moves the player’s ball, touches it or causes it to move, there is no penalty. If the ball is moved, it must be replaced.
(Playing a wrong ball – see Rule 15-3)
18-5. By Another Ball
If a ball in play and at rest is moved by another ball in motion after a stroke, the moved ball must be replaced.
18-6. Ball Moved In Measuring
If a ball or ball-marker is moved in measuring while proceeding under or in determining the application of a Rule, the ball or ball-marker must be replaced. There is no penalty, provided the movement of the ball or ball-marker is directly attributable to the specific act of measuring. Otherwise, the provisions of Rule 18-2a, 18-3b or 18-4 apply.
*PENALTY FOR BREACH OF RULE:
Match play – Loss of hole; Stroke play – Two strokes.
*If a player who is required to replace a ball fails to do so, or if he makes astroke at a ball substituted under Rule 18 when such substitution is not permitted, he incurs the general penalty for breach of Rule 18, but there is no additional penalty under this Rule.
Note 1: If a ball to be replaced under this Rule is not immediately recoverable, another ball may be substituted.
Note 2: If the original lie of a ball to be placed or replaced has been altered, see Rule 20-3b.
Note 3: If it is impossible to determine the spot on which a ball is to be placed or replaced, see Rule 20-3c.