okay, well it is (i think southeast) in "Scorpion Gulch" along the fence that blocks off the area with the bunker there should be a knocked down peice of fence that has two tall rock walls on both sides, when you go in there should be bark scorpions and giant radscorpions, there is one spot with a triangle like area with a big dark brown rock in the middle, i found the pistol on top of the rock (i think the rock has a small plant on it). i can try to be more specific if you still cant find it.
EDIT: the triangle area i mentioned is the paths, they kind of make a triangle-like shape, and it is fairly small, so you might have missed it because you were avoiding the large swarm of scorpions
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