Which drive mode was the 323 running in and which options did you select at the wizard screen?
Was the drive you added from a Linux machine?
As for unformatting, if it was me I'd put the drive in a PC and be googling for drive recovery tools in a vague hope it would recover something and be able to understand ext2/3 file systems.
Too late to give you the advice but you should have a backup of your data before attempting anything like this. It's amazing how many people fall foul of this basic principal.