It's not deleted. The world just is most likely corrupted to the point where It's unable to be seen on minecraft, I may be able to fix this but I need to download his world first.
I am sorry. There is no way of recovery... Your DAT_OLD file was completely erased which means everything is gone.... Your world was corrupted, I used data from another DAT_OLD file to see if I could see at least make the world work, it did work but I think the world might have been reset...
Where I spawned was this desert terrain south of me was a swamp region north of me was more desert east of me I dont know didn't go that direction and west was a forest region. There was nothing in the inventory so yeah I am pretty sure you will not be getting your world back.
I have an idea though, can you restart your computer from a back-up? If you have any, also I can give you the world seed if you want.
Oh shit. Really. Well you need the DAT_OLD file to have something in it so that your owrld will show up in minecraft... I guess I fixed that problem then? idk...
I guess I need to study a bit on world corruption.