It all depends what kind of partition you had. If it was ext2 or ext3, you probably just destroyed all of your inodes.
Unfortunately, when you run fsck or another program that is supposed to fix your disc, if you choose the wrong program or the wrong version, you run the risk of destroying data.
That is what happened to me some time ago when I used a very old version of e2fsck on a damaged harddrive.
You can try running the appropriate program for your archecture, but at this point you have probably done permanent damage to the partition table.
Speaking of which, if this happened suddenly, your harddrive was probably ruined anyway, and there most likely wasn't much you could have done to restore the data.
Good luck, but prepair yourself to "reinstall slack".
And next time, use ext3 so when this happens next, you can just recover the journal and be done with it.