Did some testing the other day. I went through an area and picked up every piece of loot that I found and dropped it in the same spot. Some of this was obviously player-dropped loot - a 'wet' hunting jacket in a garage (this had been there for two days as I came across it before), damp jeans in a hunting stand, etc... but most was spawned loot. I covered a fairly good-sized area, going through houses, garages, a few barns and a police station.
In one area I dropped four hats, two inside a deer stand, and two about 30m away near a tree. In each instance I dropped one directly, swapped it with one in my inventory, then dropped it again.
When I went back through the area about 45 minutes later, every single piece of loot I picked up and then dropped was gone, regardless of how I dropped it. Every, single, one.
There's definitely something strange going on, as I said some of this was absolutely player-dropped loot and I know at least in the case of the hunting jacket, it had been there for at least 2 days. So perhaps it's only when you swap something that is equipped and it drops to the ground? I'll hopefully get to test that tonight.
For now Ill update the reproducibility to random.