Good Morning, Afternoon, Evening, Night!

Yesterday evening the central heating boiler didn't seem to be working - the radiators were cold. I googled boiler settings, searched for the manual, tried all sorts of settings but Nothing.
This morning, still no heating so I rang the company that I have a service contract with, and put on an extra layer of clothing! I managed to get the hot water part of the boiler to heat, but not the radiators, so I emptied the airing cupboard and the boiler cupboard and waited for an engineer to arrive.
The engineer came this afternoon and I talked him through my theory of why it wasn't working - that the timer was playing up and the actuator valve on the heating side was broken. (My brother's a plumber so I should know what I'm talking about. 
The man listened very patiently, reset the timer, confirmed that the boiler wasn't firing up and asked "Where is the main thermostat?"
There are thermostats on all the radiators - says I.
He looked at me like I was about 10 and said, not those, the main one, on the wall.

Me:- there's something on the wall in the hall but I understood I didn't need to touch it but rely on radiator stats.
Him:- Show me where it is
So off we go and find the little box.
This time he looked at me as if I was about 6 and said its been turned down to below the temperature of the radiators so the boiler won't come on!

Then I remembered, for the first time for ?months/years I'd dusted the box yesterday and must have turned the thermostat down at the same time.
I was so embarrassed, I felt as if I really was 6.
He was so nice, told me he'd make something up in his report so that it would be an emergency call out - otherwise there would be a £60 charge.!!!

The moral of this story is................Dusting is not good for your image or your wallet.