I've recently made a clone from my failing external drive, with ddrescue. The cloning seem to be suuccesful, but when I open up the clone drive, a lot of files lost metadata.
I have only the filename and the filesize are ok.
Sometimes during the period of clone, files may disappear without any reasons, but technically it is recovable with the help of a data recovery software. Open this link: http://download.cnet.com/iCare-Data-Recovery-Free/3000-... it is a freeware and designed for data recovery caused by many reasons. It is easy and useful.