If you have emptied your recycle bin, my OH says the pic is still in computer as it is on your desktop. (he knows my IT skills so he put it in 'little' words!)
Apparently you need to go into the search facility and tell the computer to search for jpegs. It should then show you all that you have in the search results, one of which will be the desktop image. You can then export it to 'my pics' and do with it as you wish.
Hope this helps
Sam