Not hot on physics, but maybe the beer was near to solidifying before you poured, but just not quite, due to the alcohol not letting it freeze. So it only appeared to look liquid in your eagerness to get the cap off.
For a moment there I was thinking you were going to tar us Brits with an age old myth that we like warm beer
Which does actually have a certain amount of truth in it, as quite a few 'ales' are served at room temperature to allow the flavours to come out. But room temperature is a Victorian measurement (i think) whereby all houses were generally colder anyway.
Who's this Lucas chap... my fridge was made in Italy :P
Hope you quenched your thirst at any rate
