Here's one from a few years ago - at a Pneumatics Suppliers Counter in Nottingham.

Me: Can I have one of those XYZ-123/B, like the one that's on the shelf over there.
Jobsworth: I'll just look it up on the computer. Sorry mate we haven't got any, computer says zero stock.
Me: What about that one there!
Jobsworth: If the computer says we 'aven't got any, we aven't got any.

Cheers,
Rob