You were on your own and made them serve something that you didn’t want and it ended up being premeditated. Not really sure that’s any better than just being blunt and saying they were too slow and walking off without wasting £5.50 of product. In fact your lonesome, revenge timidness was pretty weak versus being honest about in the first place.
Well no.
I wanted a beer. So I got one somewhere else.
Cool story though.