It started with the laser rifle in scopion gultch (sp?) anyway. As I was running thorugh, half of the scropions were in the ground.
I checked around and confirmed where the laser rifle is suposed to be, but im guessing its under ground.
I have tried fast travling back several times to see if maybe it will respawn back above ground, but no go.
Has anyone else exp this issue and found a work around or ?

yeah it dose tat to me every now and then and always seems to be with scorpion's only? don't know why only them.
may be they have to many legs? just a idea

I also had several scorpions in the gultch get stuck in the terrain.

If you are on the PC, try this, use TCL in the console, that can make things that have rendered under or in the ground pop free. Walk around a bit with Clipping off. I have had some NPCs that have disappeared (and reported to be bugs when they do) come back too.

Just make sure you turn the Clipping back on.