Agh! This makes no sense, any reason why the worlds didn't go missing when my computer crashed before? Think that's all I have to ask now! Thanks! Any more help appreciated!
Ok. I tried that, it didn't work. So i restored that. So it turns out, whilst playing on my other world, my computer crashed. I logged back in, and THAT world was gone too, so yeah, my computer shuts down a whole lot. The save files are still there, but not accessible in the game Singleplayer tab ... Is there any way to retrieve them? Or are they gone for good?
Hmmm ... basically in the world folder, there are the following folders. '13' and 'Region'. And then 'level.dat', 'level.dat_old' ... and 'session.lock'. Hmmm. My other world's folder has no folder called 13? I tried deleting it, that didn't work. What do you mean unzip? The world folder isn't zipped, no. Do i need to like restore a previous version of anything? Any more ideas? I still have no idea what caused this!