WD 500GB External HD Missing Data. Please Advise.

Hello all,
I recently transferred an entire directory from a SATA WD500GB HD to an external WD500GB HD My Book Essential Edition before formatting my computer. I checked at least twice to make sure that the directory and all its files and folders were transferred to the external drive in its entirety before formatting the SATA drive then once after the format was complete. I am certain that this directory was there and complete on the external drive when I checked each time.
I connected the External HD yesterday to transfer the files back to the SATA HD when I noticed that this certain directory was missing. Note all other directories that were copied from the same SATA HD before the format were still there and complete.
I am certain that this directory was there before and after the formatting and that I did not delete the directory from the external HD. Also the amount of free space on the external drive shows that this directory is not present. i.e. the amount of free space present on the external drive shows that the amount of space that this directory took up is now available.
I have run searches and checked for the hidden directory in the external HD but have found nothing.
Has anyone ever had a similar problem with this type of external hardrive (WD My Book Essential Edition 500GB (the one with the blue light))where data is there one day then gone the next? If so has anyone found any solutions or suggestions what what I can try to do?
Thanks in advance.
-Dietrichias

I own the older revision MyBook and a newer one. I've never had this issue nor heard of it.

Honestly, I don't see how it is possible for it to just vanish, it doesn't make sense. You could try other computers or (and this next one voids the warranty!) remove the drive from the enclosure to make sure it isn't a problem with the onboard controller.

Either way, I really don't think there are any files out there.

I do have one question though, when you formatted the computer, did you have the external drive connected? If so, there is a slight possibility that it got nuked in the process...

Yeah I also have the older (green circle) and newer (blue light) versions of the MyBook and Ive never had a problem with the older green one. Also the new blue one (the one with the issue) is fresh out of the box when I used it to transfer these files.

I am certain that all the external drives were disconnected from the PC during the format. Again the files were present after the format when I checked.

I am also certain I didn't physically damage the drive, or delete the directory in question.

*The only thing that I can consider being an issue is that when I went to check the files most recently when I realized that the certain directory was gone I used a different USB port. Could that have been an issue?

I have never encountered a problem like this before where files just seemingly disappear.

Thanks again for your help.

I still don't understand how they can disappear. Honestly not sure what to tell you besides trying to run a recovery program on the drive itself. If that fails, files are gone, not much you can do about it.

For now though, don't write anything to the drive until you confirm whether the files are there or not.

Check out the following thread, they make a few suggestions. Some are free some are not, see what works for you.
http://www.ocforums.com/showthread.php?t=612886&highlight=file+recovery

If you can pull your files off, great, get them backed up and try to duplicate the issue. If not, see if writing files out to the drive does the same thing as before.

Okay great! I will try these recovery programs over the next few days and I will let you know how it goes. Thanks alot I really appreciate the help!