Re: @ CD under the keyboard
"This reminds me of the stories in the 80's and 90's of users 'missing' the floppy or cd drive slot and a service engineer finding a neat little pile of disks inside the machine.
A very slim chance, but maybe that's what happened here?"
Yes. How about the CD wasn't properly seated in the CD drive and the CD got pushed under the keyboard.
I've just taken a look at a Dell laptop and you'd need a bent or loose case, but it looks possible.
So, some sausage fingers in the HO looses a CD inside the laptop and fails to own up and send the laptop for repair to get the CD out. Or they'd been stiffed with a money grabbing support contract and a repair would cost more than a new laptop. "It costs too much to get the CD out - just make another".
It looks like another example of not following the rules about documents with protective marking. Okay, the data was encrypted. But the CD was still marked confidential and should have been handled accordingly.