The game deleted my world

So i logged in yesterday to find that you guys Updated the game, thats Great. However upon me and a friend sinking 12 hours in a map and checking the New Nether Update out i took a 3 hour break. Upon me returning to the game, i noticed that my save was not there which it was before i made sure. My map name was called Last. Or maybe called Last world. Either way i would like my map please.