External HD Accidentally pulled out of computer
I know this is an old thread but I have just encountered the problem yesterday when I accidentally knocked my external drive USB cord off.  I ended up with the same problem in this post.  What I did was connecting the drive to a windows machine and it will automatically detect and fix the errors.  It's an annoying solution but it worked.  I just wish Apple will have some kind of safeguard procedure against things like this from occurring, especially with most people backing up their life onto an external drive.