What I did was squeak. My panicky 'eueuh, eeuh, oeoh,' squeak.
It worked though. He stopped and took my card. I just left feeling a bit silly.
Anyway I got to work and was in need of a cup of tea so put the kettle on, got the teapot and the teabag ready, found a mug I liked (I'm very particular about the shape of the mug I use), went to the fridge to get the milk to discover - shock horror - there was none there.
I couldn't believe it: there is always milk in work left over from the Sunday morning. I opened the fridge several times just to make sure I hadn't missed it but it definitely wasn't there. I sighed and poured myself some squash.
Later on I had to begin battling with the website and I really couldn't do that without tea so I popped to the shop. I was only gone five minutes and when I got back I put some milk in my cup and then took the carton to the fridge, opened it and - found a carton already in there!
There were no cars in the car park but I crept into the hall and looked around. There was no obvious sign or sound of anyone. I returned to the fridge and looked again: definitely two cartons there.
And this was the moment when I seriously wondered if I might be losing my mind.