glass thicket
If you close the inventory with an item on your cursor, the item remains there but has no UI indication.
If you left click on an NPC it will open the item give window.
REPRO:
Complete a quest up to hand in.
Stand in front of NPC for hand in
Open inventory
Click on item to hand in to pick it up
Press i to close inventory
OBSERVE no indication of item on cursor
Left click on NPC
OBSERVE item give window
Give item to NPC
OBSERVE quest completion confirming item was given