Hi dallasm,
I made some tests, and I experienced a problem, which is not related to my plugin specifically, but it's a WP behaviour.
If you drag a widget (any type of widget) from a sidebar to the "Available widgets" panel that widget is killed and not recoverable in any way, even if when dragging it says "Deactivate widget", not "Delete widget" on the box title.
I would expect that the "Available widgets" panel should not be a drop target for widgets when dragging them.
Is this the same problem you are experiencing?
P.s. Thanks for Rich Tax editor mention, it sounds interesting.