Lightroom export action made images disappear from disk

My images have been stored on a networked external drive for years, with no problem.  On August 16, I processed a new batch of images in LR CC and exported them in batches to different designated existing folders on that drive.  Some images made the trip.  But most, exported to several different subfolders within one root folder on the same drive, disappeared.  What is more the whole root folder and its contents (2000+ images) have also disappeared. 

Two lengthy screen shares with your tech support did not find them, even though an old LR backup was reinstalled (on the wrong disk, btw).  The images do not show anywhere in Windows Explorer or in Adobe Bridge or in the Recycle Bin.  It's as though LR CC actually ate them!  A local tech service will run the disk through a machine for $50, to see if they can be retrieved, plus $500 more to retrieve them... Can some high level Adobe LR expert help me find them?  LR CC seems, in fact, to be the guilty party.  Thank you for your consideration. Jeanne Tifft