While dumping items out of your inventory using using Control Q on Single player your held item will get thrown in addition to the item your hoovering over. On Multiplayer your held item is Deleted. I replicated this bug consistently across Multiplayer and single player in both 1.14.3 and 1.14.4. I have attached a single player demonstration video.

Edit - after re logging a few times on the server the item reappeared on the ground this is still annoying though because generally people through large amounts of items into lava.