Any chance you won through damage from a liquid-antimattered creature or something to that effect?
I see that bug quite frequently in that situation - it happens when you manage to win in one of the situations where you gain health at the same time they take damage, and the death check occurs before it resets your current HP to max HP, so you win with (say) 104/100 HP. This is quite easy to observe with LA - the unupped oracle prediction decks for akebono/obliterator produce this effect most of the games I've EM'd with them.
Even if it wasn't a LA-based situation, I'm still willing to bet the curHP>maxHP bug/feature is to blame here. Unless of course you weren't gaining any HP at all during the damage-resolution routines, in which case I have no idea.