The title, explains it mostly, but essentially I've spoken to many people, who have last a tent or a barrel on 0.58 experimental, even though their trucks which were where the tent/barrel was did not get wiped. We deduced that it cannot be due to players taking the tent/barrels and leaving due to the number of reports of this.
Having spoken between a few players, we decided that the only thing the links all of the camp sites wiped, is that they were in an approximately ~1km radius a helicopter crash site. We hypothesis, that since a helicopter crash site wipes items around it after despawning, that there could be a bug, in which this is extended over a ~1km radius, something that is also found in towns at time near heli crash sites.
Camp sites that were not within a ~1km radius did not suffer this wipe.