Although Rule 27-2b states “the player may play a provisional ball until he reaches the place where the original ball is likely to be”, Decision 27-2c/2 provides that the player must inspect a ball which is believed to be his original ball. [Don’t interpret the Decision narrowly to assume that the concept only applies to balls near each other.]
[The proper ruling is dependent on whether it is likely that the ball in the rough could be the player’s ball. If it is likely to be the player’s ball, the player is not permitted to proceed with the provisional ball without identifying the ball in the rough. If the player plays a stroke with the provisional ball and the ball in the rough is the original ball, the play of the provisional ball would be play of a wrong ball.]
In the above incident, the statement “I think I see your ball ahead in the rough” is sufficient to conclude that a ball believed to be his original ball has been found. As taught in Decision 27-2c/2 (and Decision 27-2c/3), if a player is advised that his original ball may have been found, it must be identified by the player.
In the case above, the player has played a wrong ball, incurring a penalty of two strokes, and must continue play with his original ball.