Reaper loot disappearing when I leave the game after killing it

I never really thought it was a game issue and a saving issue that I was having until I recently talked to some people about it. I killed the reaper about 5 times with a few buddies of mine but my loot kept disappearing everytime I left the game and came back. This is pretty annoying especially because I got some pretty good loot.

did the loot disappear in the reaper, before you picked it up (then left the game, came back, tried to pick it up)?

Why did you leave the game and came back? Unintended by crashing?

Which system do you play on?

Have you been host or guest?