From our rules chairman, Janice:

Searching for and Identifying Ball – Simplified Version12-1. A player isn’t necessarily entitled to see his golf ball when hitting it. While searching for a ball, the player is allowed to move or bend long grass, bushes and similar objects, as long as he doesn’t improve his lie or clear a path for his swing while doing so. If a player believes his ball is covered by sand but he can’t identify it, he may brush away sand to identify the ball. Afterward, he must replace the sand to recreate the original lie. If looking for a ball in a hazard, the player can remove loose impediments but must replace them to recreate the original lie after identifying the ball. A player searching for a ball in a water hazard can use a club to probe for the ball (in murky water, for instance). If the ball is moved during the search, and the player intends to play the ball from the hazard, he must replace it (without penalty). While searching for a ball in or on an obstruction or abnormal ground condition (e.g., casual water), the player must replace the ball if it is accidentally moved, and he plans to play it from that spot rather than take relief. Penalties for violating Rule 12-1: Match play – loss of hole. Stroke play – two strokes. 12-2. If a player thinks a ball might be his but isn’t certain, he can lift the ball to identify it after telling his competitor he intends to do so and marking the ball’s position. The ball can’t be cleaned any more than necessary to identify it. If the ball is his, he must replace it in the original spot. Penalties for violating Rule 12-2: Match play – loss of hole. Stroke play – two strokes.