Recovering Accidental Storyboard Deletion

You can find the Storyboard file in the Base.lproj folder,from there you can just drag it to Xcode

Even if you deleted your main story board, it would be there inside the folder called Base.lProj
(This folder will be in the folder where your source and header files lie in the normal case.)

So go to Xcode. Right click in the Project navigator in the left side tab and add these files to the project again.

If it popped up that means you can find it in your project folder. Just look in /projectName/projectName/Base.lproj. The storyboard is there. You can drag it into Xcode and its as good as new.