http://cloud.steampowered.com/ugc/577805138469819320/E54894BDD362619FD3A...
I killed an Alpha Wolver here and it managed to glitch out of the walls during it's little death spin.
And then, http://cloud.steampowered.com/ugc/577805138478336355/3BB30E993AEEAA413A0...
These things happen. Try walking around the area and you might pick it up. Or it might be a hard blown glitch and the devs will have to fix it.
I had to pick up a heart that was floating in the air once.