This happened to me too...since then I've started backing up my saves, but it hasn't happened again yet, (backing up my save my going to start, searching "run" running %appdata% clicking on minecraft, and copypasting my save folder to documents...for windows of course) I know this doesnt answer your original question but its what I do now.....still can't access my old world either :/
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In Soviet Russia, Creeper's home get blown up by you!
"...no, even then....Creeper still f***s everything up..."
In Soviet Russia, Creeper's home get blown up by you!
"...no, even then....Creeper still f***s everything up..."