DMcG:
My nearest example to that was a computer clitch, not a human one (or not the sales staff anyway). I wanted to buy an item, found it on the shelf and took it to the desk. "Sorry, the computer says it's out of stock, I can't sell it." "But it's here." "I know, but it's out of stock." Once we got the terminology sorted out, it turned out the computer system simply would not let them sell an unstocked item, no matter how much you pleaded with it. I knew it existed, they knew, but the computer knew best. A bit like Rapaire's books in reverse, really.
"If you're sure that this item is out of stock, then this must be one I brought in with me. You don't mind if I take it back do you?"