The creativity itself and the process thereof exists in the "now", sure. No argument there.
But the
result - the story, the music, whatever - doesn't exist in any useful form until
after it is created; when the music reaches the ear of the listener either then or, via a recording, later; or when a written story reaches the eyes of its readers. And here the result - i.e. the end output as seen/heard later - is what we're talking about as being story.
Put another way, I could (and do) have story ideas in my head right now but until I get on and do something with them that's all they are: ideas. And if I put down some notes on those ideas that's all they are: notes (or, to use a sometimes more accurate term, game prep

). But any story that might grow out of those notes doesn't yet exist.
There's another possible delimiter here: that a story doesn't functionally exist until someone else other than its creator(s) has access to it via reading it, hearing it, seeing it performed, or whatever means, even if that access is never used.