ffs can't find superblock

[mortee <mortee.lists%kavemalna.hu@localhost>]

Hello!

I had my NetBSD 5.0.1 i386 box crash, and now it can't mount its backup
hdd. fsck keeps telling:

$ sudo fsck_ffs /dev/rwd3a
** /dev/rwd3a
BAD SUPER BLOCK: CAN'T FIND SUPERBLOCK

I've already tried specifying a few other possible superblock backup
locations using -b, but it reports wrong magic number for each one tried.

Is there any other approach I can try to get to my data? Anyways, how
can it happen that a crash invalidates any possible superblocks on a
drive, which is not physically damaged, and still has the correct disk
label on it?

thanks
mortee