"Have you found something a user swore was lost?"
Many many times. Most common one is people moving the mouse when they go to double click on a folder. The result is them dragging it and moving it into another folder. The operation happens instantly and suddenly their folder is "gone" and they panic.
As for losing emails, people who create folders and use the Deleted Items as their filing cabinet. Back in the days when we had an in-house Exchange server with a hard storage limit I was coming close and used GPO to clear people's deleted items when they closed Outlook. Oh the wailing and gnashing of teeth that happened after that and people complained that they I had deleted the emails they wanted to keep.