It depends on how it was 'formatted over'. If you formatted it as,
say, FAT, there is a slight chance that not everything is lost. There
are copies of the super block at regular intervals, see the ext2
documentation for details. Since some of the inodes might be overwritten
as well, you cannot expect complete recovery.
If you formatted it as ext2 again, then you most likely destroyed all
meta-information. The superblocks are in the very same locations again,
and the inodes are all erased. Prepare to restore from tape.
Regards,
Martin