iMac Hard Drive Went Fubar...

I suffered a problem with my IMac hard drive.

My main volume encountered the "Invalid Sibling Link Error."

Fortunately I was able to access the drive via terminal and copy my most essential files off and safely store them away.

I purchased an external drive and installed MacOS X on it, and I then downloaded DiskWarrior.

I installed DiskWarrior, and I ran the repair program on the effected volume and disk warrior said that the restoration was successful.

However when I rebooted, the computer can not detect the actual physical disk anymore.

I restarted a couple times and the disk reappeared (in the Mac OS X installation utility). But I haven't been able to repeat this.

I do not hear any clicking sounds that would indicate a physical device failure.

At the moment I really hope that I can get this drive online (if not for restoring my previous OS, but for retrieving the rest of my documents)

Anyone have any suggestions?

I've learned my lessen though, now that I have an external drive, if I get my main drive back online I will use Time Machine religiously from now on...

I would say, keep trying to see if you can get the HD to appear in disk utility when running from the DVD. Go and see if you can run the permissions check and repair and see if you can verify and repair the disc. See if it passes the SMART test. If it fails, it would seem the HD failed.
The clicking is a common tell of bad HD but not the only.

Hopefully you can get the rest of your data in the meantime. And you can get Apple to replace the HD if the iMac is still under warranty. Good luck.

Ok, so the drive appeared in the OS X install DVD and the SMART test passed.

But then once again the drive is not showing up, and I have yet to get it to appear again.

Does you know what could be happening?

since you have backed up the disk, have you tried a resh HFS format with Disk Utility?