I was playing Fallout 4 and got to the Corvega Factory and killed some not completely random trash mobs. It was difficult to get to them and loot them immediately though, and after I tried to loot some other enemies and stash some stuff in some containers, the corpses for the raiders at the factory had already disappeared.
Now this raises a question: In general (whether at this location or any other), can a non-named mob ever drop something critical – in particular, something that cannot be obtained later off of another mob? If so, will that guarantee their corpse will stay there indefinitely until the item is looted?
Best Answer
No, you won't get critical items dropped from 'random' mobs.
In fact I've only seen 'critical' items as you describe them, dropped in fights where it's obvious something has dropped as there is a cut scene or something prior.
I didn't try leaving the areas mentioned, but I'd be surprised if you could loose any items in this way as previous games have always generally dealt with this problem in a sensible way (non-rotting corpse, item remains after rotting, etc).