Forum:World disappeared after pc crash?

So i was hosting a server with me and my friend, and then i started getting like 5 fps (i normally get about 45-60) after about 2 minutes i got fed up and decided to restart terraria. so i pressed escape to open the menu to press disconnect and it would not process that i pressed disconnect. after about 2 minutes of trying i had to alt+f4 my terraira because it was lagging my whole pc out. when i restarted my terraria, my world was gone from the list yet even though i only had four worlds on the list now, it still would not let me create a world.so i tried the first thing that i thought and deleted a different world, then go into the map folder and change the name of my original world that had disappeared(which was still in the folder) to the one i had just deleted. that world then wouldnt work. i really need help because i put allot of hours into my terraria world and im thinking about quiting terraria. please help!