On the quest "A Final Death for Gravity" it looks like if you don't grab the boots off of the corpse right away, when you come back the corpse is gone. I ran around looking for where it could have gone and it looks like it's under ground now. It used to be on the ground in front of the giant lift, but now the only marker for the quest I see is down underneath the lift, which you can't get to. See the attached screenshot. 

Leaving the planet and coming back re-set the bodies location. I was finally able to loot it, but before I was able to leave the body was underground as seen int he image I attached.