Snapshot 16w15b Saves

I made a save on minecraft in the 16w15b update, I made a massive house and save and quit the world then exited. I shut my laptop down and in the morning I woke up and went onto my laptop and started up the game to find my new save had disappeared, This is rather annoying because I spent 2 hours on it, I made a new world and dragged the insides of my world into the new one and that world disappeared. Is there a way to fix it?