Lost files after sync

If you cannot access your files from the USB hard drive or the WDTV hub, it is possible that the data is corrupted. To be sure, try scanning the USB hard drive using a data recovery program, using Google you should be able to find several options, also see if the following link helps. Let me know how it goes. 

http://community.wd.com/t5/WD-Portable-Drives/MyBook-Files-Deleted-Can-I-Get-Them-Back/m-p/370881/highlight/true#M9715