Missing with a Thrown Weapon
If you miss on a ranged attack with a thrown weapon, the weapon lands in a random square or grid intersection as appropriate near your target. To determine where it lands, roll 1d8. This determines the initial misdirection of the throw, with 1 falling short (off-target in a straight line toward the thrower), and 2 through 8 rotating around the target creature or grid intersection in a clockwise direction, as illustrated in the diagram above. After you’ve determined the misdirection of the throw, roll 1d4. The result is how many squares away in that direction the weapon lands.
For example, after a missed ranged attack with a grenade, a player rolls 1d8 with a result of 1. This indicates that the grenade’s initial misdirection falls short of the target intersection. Then, the player rolls 1d4 with a result of 2. This determines that the grenade actually lands at an intersection 2 squares in front of the target intersection.
Source
Core Rulebook pg. 245