I did that once to myself: Instead of selecting 16GB flash disk as target for the image, I have selected an external hard drive.
Being lazy (hopefully, I had nothing important on that hard drive), I used TestDisk and I was able to recover majority of the files there. Directory structure was mostly lost, but this did not matter.
To the OP: If you can afford, borrow / buy a hard drive big enough to make first an image copy of the corrupted disk. That copy would (and will) take ages to execute, but you will have peace of mind that you can try as many recovery tools as you like.
The way I recovered my hard drive: I ran TestDisk under Linux, and it operated on a file image of corrupted disk.
I downloaded the creation media file and missed the small warning that it would overwrite all files on that drive. It shows the FAT32 30gb file in disk management and 400+ of unallocated space. I believe it was only originally formatted and one partition, I was able to recover about 40 jpegs.... Would it best to recover partition then data or just data etc? I tried a couple programs that google gave and not having the best luck, I realize its my own mistake tho lol