How to Reproduce:

• Start a new world.
• Run a background program to use up just over all your available memory.
• Wait for Minecraft to close the world for you, saying that there is no more memory left, and give the option for you to return to the title screen.
• Wait a few minutes.
• Return to the title screen, and notice that the panorama is rapidly spinning.
• Go into singleplayer, and notice that the world you created earlier is now missing from the list.