Connection Lost: Timed out in singleplayer world

I was playing in a singleplayer world and somehow managed to get the "Connection lost: Timed out" screen to show.

When I clicked back to server list it actually took me to the multiplayer menu, which is strange but I think that's a separate bug.

I have no idea what caused this or why so I can't put reproduction steps but I think it's a weird snapshot-related bug.