That also happened to me one time on British Air. I was not with my partner who was in Business class, and so they put me with her. What a nice break that was.
I am fortunate enough to have flown in business maybe a half-dozen times, and it is a world of difference. But not enough to justify spending an extra $2000 for it.
I wish I was wiser about getting upgrades, etc, but I have never mastered any of that.