Ok, so this is not really drag & drop. Drag and drop is for dropping stuff onto other widgets, when the drop is detected by a widget’s onDrop implementation.
I believe what you’re looking for is OnDragCancelled since we’re dropping into the world, rather than detecting another widget container, right? Something like this:
The above would be implemented in the Drag Operation itself.
In short: the onDrop does not work if there’s no widget to drop onto.