In Minecraft: Windows 10 Edition, I created a world like any other world. I kept the world less than a week. Soon, after a few days, I turned on my computer, played Minecraft, seeing the world deleted! It's strange to me because it didn't happen to other worlds and I kept it for about 2 weeks! I'm not sure what caused this. This happened after beta by the way, so it couldn't have been corrupted. Also, it's okay if you can't bring the world back.