After the fact, the other players noticed and pointed out that I “could have won” if I’d noticed, but since I kept on playing, we all decided that I’d missed my opportunity. Should I actually have won?
A: We would rule that you won. In Fluxx it is not required that you notice and claim victory. The conditions existed such that there was a winner. Everyone knows it happened; no-one is actually contesting that the win conditions WERE in fact met.
Just because it took a little while for the winner to realize, does not negate that fact: there is a winner and the game is over.
Now, having realized it belatedly, I’d say that if the consensus between ALL the players (including the winning player) is to keep playing anyhow, and ignore that, that’s up to them. But officially, were it a tournament, for example, we’d count that as a win.
Now, if the conditions happened so long ago in the game that people can’t quite recall what happened, and the win is uncertain, that’s another case. Then I’d say you’d have to keep playing. I guess if they’d never pointed it out to you, then the win conditions would have faded into obscurity. But I’d call deliberate non-acknowledgement of someone else’s win cheating.