Minecraft world gets deleted?

So i was playing minecraft and my computer ran out of battery and went into sleep mode. i quickly plugged it back in and when i came back on to minecraft it showed minecraft but everything was the wron color and i couldn't move. i took out the battery and completely shut down and when i re-booted my world was deleted. i worked for months on that world and its happened to me 3 times and its making me think i should quit minecraft. My computer does not have any viruses and this has happend to me 3 times now and i dont know what to do. when i go into minecraft. and i click on the saves folder it says my world is still there but its not on the minecraft main menu. how can i recover my worlds?