Argh, oh man, that does happen to the best of us! Model everything, make the whole thing work... then BAM! Absolutely no story to go with it. You're definitely not alone. It's happened to me too. I tossed out the whole game, characters, backdrop and all... so I know how you feel.
That feeling at the pit of your stomach when you're like, "oh nuts, I did all of that for nothing"? Yeah.
If it helps though, it does look gorgeous - so don't give up on it if you're still willing to plod along post-jam to add more stuff. At least you have a demo up in time for folk to get a look and feel of it. That is something! Well done!