I was bored and was playing music discs on creative mode. I heard that playing discs 11 and 13 together was supposed to make a creepy noise. I tried it and shortly after, it crashed. Every time I tried to pull it back up, it will show the Minecraft logo for a few seconds then it will close out and disappear. I did some research and read that uninstalling and reinstalling the game will fix the problem. I tried that and now all but one of the worlds have disappeared. This has led me to believe that it is a bug and needs to be looked at.