Minecraft froze and world no longer exists

While changing from a screen shot back to minecraft, minecraft froze and that world can no longer be found on my saved games. It is as though it deleted itself when it froze. This world was saved on my wife's xbox account but no longer exists. All other saved worlds are still there. We have played this world together since the aquatic update came out and have had to issues no this point.  Please help us get our world, "7 Wonders," back!