I've had this issue all day today.

They don't disappear. I did some testing when I noticed them going missing, The objects seem to go back to the location you originally picked them up, But then after some time, maybe due to server lag? they will move to the location you dropped them. The time it takes to move to the new location can differ from person to person.

I don't think items dropped in vicinity go back to their original spawn, they go to where you placed it, its just lagging for a minute or two. Do a test where you go to a road or flat area and drop a large or easy to find item and you'll notice its not there but wait and it will appear after a minute or so. I've done this with multiple items and cases in different locations. v.113822

I Already tested this. They do return to their original positions. I lifted a hat and an orange from a house, walked out the door and could see their original positions in the doorway. I placed the objects on the road and seen them appear inside the house again, then after about 60 seconds they moved to the road..

will try seven's hint tomorrow.

we had the impression that after dropping (aka losing) an item into the vicinity it just takes some time for the item to actually appear in the vicinity.

usually ~60s, sometimes several minutes.

http://feedback.dayzgame.com/view.php?id=890

Yes I can confirm the delay. We tried it again yesterday and thought the stuff was gone again and then suddenly after about 20 seconds they appeared on the ground. It's definitely not the dropping through floor bug, the items were perfectly on the floor, just really delayed.

It does not disappear, it simply takes a very long time before it shows up. The only time it disappears is if it falls through the floor of a building, but that only happens in a handful of building types.