[Grml] recovery from mkfs error?

I've heard grml comes with forensic tools, and so was wondering if there's anything in the toolkit that might help me recover from an unpleasant mistake.

Trying to reformat a usb thumbdrive, I overlooked the fact that /dev/sda was my 160GB external hard drive (ext3), and that the thumbdrive was actually /dev/sdb. I issued this command:

mkfs -t vfat -I /dev/sda

The most important stuff was backed up, but there is some pain involved. Any suggestions (yes, I know... PAY ATTENTION!!) or pointers much appreciated.

Regards,

John