I dont know

I think this may be what has happened...

You may have flashed someone in or out a junction during daylight/twilight while no lights or only side lights are on, but pulled the stalk to far towards you, turning on full beam, but that wont stay on till the main beam headlights are turned on, so when you turn on your headlights straight away full beam is on.

Be a bit more gentle when flashing

nehh .. he was just looking for the dipped beam light on the dash, he thought it would be different from the sidelights.

Facts: Position 1: Sidelight turns on, light on dash comes on.
Position 2: Dipped beam turns on, lights on days stays on and the same
Fogs have different lights on dash
You can flick or toggle main beam with your stalk depending how far you go, you feel it click on a toggle. This will enable the main beam as well as turning the blue light on the dash. I think that's end of. hope this helps.

You might wanna check your handbook to fully understand what is going on =)