Not a problem, although quite a few of us (including me) experienced the Live changing the byte size of an ISO to “0 bytes”.
WD says they are looking into this, so meanwhile, the best course of action is to always unmount the attached drives before turning off the WD or removing a drive. Also, HAVE BACKUPS of the ISO files!
Perhaps your drive was not completely finished adding the files, so turn of things and then recheck ; maybe even connect the drive directly to the PC to check for the files presence.
