I guess you played the 10 min game. It is called informant chess, which is not, as i thought first some kind of "beginners" chess.

In fact it is a variant of chess where you can indeed change the pawn at the second row. Not into a queen though, but into a bishop, horse or castle. Or remain a pawn to become a queen after one further move.

I think that's what you played. I a regular game nothing of this sort has ever occured in a game i played/watched. And believe, that were quite a few :)