I Was playing in my world searching for emerald, spent hours searching and noticed that my game started to lag immensely. I saved once worried that my laptop was due for an update (whenever it needs to update everything starts to lag) I saved my game and quit so i wouldn't lose progress. I immediately returned and continued onwards and made it back to my base. I went to sleep in game and saved & quit once more as the lag started to get really bad. I quit successfully but my game froze afterwards and I couldn't close the game and was forced to manually turn off the entire laptop. I turned it back on and tried to return to the game I got a message to sign in to my microsoft account, and then there was a notice that the game had been updated to (with updates including fixing the generating world phase) though I believe this notice may be wrong (since I'm sure i saw it a while back with the same fixes) I continued onward and got to my worlds list and the world I was playing on a few minutes prior when the lag occurred is no longer there. I had a copy of the file set to creative, but not the original survival world. 

I think the world still exists in the saves on my computer, but when i tried to verify if it was, noticed that the name of the world was left blank, and the world icon doesn't open.  

I've attached some files that i think might help, though i'm not sure.