There are two possible ways that I can remember:
a) Using Knife ST.
You need to load Knife ST, put the disk image in with the deleted files in Drive A: and a blank image which matches the same disk size in drive B: There is an option to undelete files from one drive and copy to another.
b) Using a hex editor
Alternatively, assuming you haven't written any files back onto the disk, you can use a hex editor to change the byte after the filename in the FAT table with a hex editor. If this sentence doesn't help you, then use Knife ST as per above. This can be either an ST hex editor running on the disk image, or via WinHex under Windows.
My main site: http://www.mug-uk.co.uk
- slowly digging up the bits from my past (and re-working a few): Atari ST, Sega 8-bit (game hacks) and NDS (Music ripping guide).
I develop a free Word (for Windows) add-in that's available for Word 2007 upwards. It's a fix-it toolbox that will allow power Word users to fix document errors. You can find it at: http://www.mikestoolbox.co.uk