I think that there is a glitch in the re-listing system again. Unless I'm going mad. I've noticed this a few times over the past couple of days.
I do the relist / delete thing. Revise my new listing and then notice that the old listing was not deleted. Double checked by back clicking and found that I had hit the delete box and that the system message had been that the item was deleted.
But it wasn't.
Just happened again with some stamps that I was relisting.