Need back a lesson that I just deleted

It appears I can't delete a team folder without deleting the lessons too, and I can't move lessons out of a team folder into a private folder either. This morning, I wanted to remove a team folder, and the prompt warned me lessons would be deleted too. Once lessons are in a team folder, they don't appear to be movable to a private folder. So I created a new team folder and moved one of the lessons from the first folder to it.

I thought if the lessons was going to be deleted, I could recover it from the Deleted area or catch the Undo if it looks wrong. I deleted the new team folder, saw the one lesson disappear (from the My View area), and clicked Undo. But it's gone. Undo did not catch the deletion, and the lesson isn't in my Deleted area. 

Can this lesson be recovered? Why must lessons be deleted when deleting folders, especially team folders which are meant for sharing?