New member, hope someone might be able to help as I'm not finding much with searches here (could be that I'm using the wrong search terms, I don't know). Anyway, here's my issue and if anyone has any advice I'd be grateful to hear it.
I have a Dell Latitude E6400, fantastic rock solid machine, and I just finally got myself a slightly larger capacity hard drive for it (a Seagate Momentus Slim 250GB, the 7mm drive, someone gave it to me). The original factory drive is a Seagate 80GB drive, never had one issue with it, not one problem with testing and diagnostics, S.M.A.R.T. status was (up till what I'm about to describe happened) perfectly clean, not one attribute out of place.
I was using the Seagate Disc Wizard (Acronis True Image made) to do a cloning operation from the 80GB to the 250GB and I had the 250GB drive mounted in the laptop already. I had the 80GB drive attached using an eSATA-to-SATA cable to the drive's SATA port and I had a discrete power supply for the drive in use (one that I use with external drives, it works fine at this point so it wasn't the power supply).
I did the cloning operation and everything was fine, booted up off the "new" 250GB drive and everything was still fine - the 80GB was detected as a secondary drive once Windows was up and running (Windows 7 Pro x64 is my OS of choice). I could open the 80GB using Explorer and checked it out with HDTune just before this "thing" happened. Again, the drive showed perfectly fine with no issues.
I then decided to remove the 80GB and me being the idiot that I am I simply unplugged the eSATA cable from the drive itself and... well, that was that. That's all I did, seriously, I simply unplugged the eSATA-to-SATA cable from the back of the 80GB drive - power was still going to the drive from the discrete power supply, so that wasn't the problem. I wasn't powering the drive from the eSATA port (but this port, with the right cable, can power a 2.5" laptop drive externally).
I shut down, removed the 250GB drive (which was internal at that point), put the 80GB back in the drive bay and booted the machine - obviously the BIOS is now telling me the drive has a problem and it needs to be replaced.
So here's my question after that wall of text:
Can just unplugging an SATA, or even eSATA, cable really just kill a hard drive that quick and easy? I'm kinda pissed about this but I have to blame myself for not doing the proper "Safely remove hardware" step that I
typically will do before removing a drive whether it's eSATA attached or USB, doesn't matter. This one time that I simply disconnected the drive and now it's totally dead. SeaTools for DOS gives me a code of 9BA89C43 and I'm about to email Seagate over it but I'm sure they'll say the typical line of BS: "It's an OEM drive, we don't support it, and no we won't even tell you what that code means either..."
It's not that I lost some data at this point, it's that I'm flabbergasted simply unplugging a data connection on a hard drive can kill it. I can imagine if I'd yanked the power cable that could cause problems with the heads/swing arm, etc, but disconnecting the data cable can do it to?
Sorry, I'm wordy. If anyone has any advice, I'd like to hear it. I can live without the 80GB drive but if there's any chance of making it functional again that would be awesome as well. Just a bit mind boggling to think this happened or <gasp> it could happen again with some other eSATA attached drive.
Needless to say I'll never do that again.

Thanks for reading...