Not sure if this helps... But i noticed that some servers started to do reset on persistance files, in order for the loot to respawn.
May 11 2016
I dont know if its the same matter... but i cant find a single weapon when running around the map with my friends.
We enter in every single house and sometimes split to cover more cities at the same time. And still nothing.
We play on private hives most of the time, oldschool/monstergaming and so on...
After server restart on monster gaming the loot started to spawn again for a couple hours then stopped.
I played experimental and i didnt had this problem. Tomorrow i will play on public servers to see if the same thing happens.
The weapons doesnt disappear. The weapon is dropped to the ground randomly it seems, from time to time.