Affects Version/s: Minecraft 16w39c
Fix Version/s: Minecraft 16w40a
Steps to reproduce:
1. Place any right-clickable block or item into any slot of the hotbar
2. Go to the Survival Inventory tab
3. Drop the item (Either by dragging it or pressing Q)
4. Exit the inventory
5. Right click on the ground with the same slot the block/item was, you should see that the item is still saved in that slot.