Corrupt NEF files - so sad if images are lost

Were you copying or moving?  I NEVER move files off a CF card.  I simply use the Finder to drag-and-drop the files where I want them.  I never understood the idea of using software to move/copy files.  It just seems so much easier to drag-and-drop.

If you were copying, the original on the card should still be there.  A moved file may also be recoverable, but you will need software to do that. Whatever you do, don't put the card back in the camera!

I would suggest reformatting the card in the camera every now and then.