Minecraft world gone What to do?

Moin I play on Xbox Minecraft I started Minecraft and now a world is gone that I played with a friend what should I do now? Do you know something?

Restart Xbox, nothing more is possible, if the world is not there, it is not there.

I'm sorry for you, already had the case too

The first tab where all worlds are listed, just go down there and click on synchronize old worlds, that might help