I cant really offer any suggestions sorry, but I am curious how one accidently formats a harddrive ? :-) You either have to use a shell and type stuff, or use an icon, which prompts you if you're sure and then asks for volume label, if you want disk cache/trashcan/etc.
These things arent easy to do by accident :-)
Or does OS3.0 not have these things ? It's been a loooong time since Ive used 3.0.