My world is gone, kind of. I can't play it, but in the .minecraft file, it is still there. I tried taking it out of the folder and putting it back in, but the world still doesn't show up in the launcher. I tried copying it, but neither the world itself or the copy shows up. 

I don't know what happened, but I know what happened beforehand or any other details. I had turned off my computer with a paused game. The game itself was in the newest snapshot 20w12a, it was survival. I don't know if it happens with creative too, but I'm too scared to test it out. After I had turned off my computer, I turned it back on around 45 minutes later, the computer had restarted.  I launched that game back up, but my world wasn't there.

I really don't know what happened, but I hope I gave as much detail as I could have given. Thank you for your time.