What happened to my level? Fatal Error

How's your level "not deleted" but "gone" at the same time? Please clarify.

Note: It's a long shot, but try closing unity, deleting your "Library" folder then reopen your project.

If Unity crashed, then I'm sorry to say that whatever you had done between the last save and the crash is now gone. Unity does not save anything during a crash (how could it?).

In order to prevent losing a lot of work in the future, remember to press that Save button (or pressing ctrl-s) every once in a while.

Because I didn't delete it, I opened up unity after it crashed and the scene is just completely gone, no trace anywhere.