From Divinity Engine Wiki
- query ItemGetOwner([in](ITEMGUID)_Item, [in](CHARACTERGUID)_Character)
Returnes the Owner of the _Item as _Character, which is the last character to have the item in their inventory. This can be overridden through ItemSetOwner.
- Success/Failure: Fails if the _Item does not exist.
- _Character: The owner of the item.
- An item's Owner is cleared when that Owner dies.