and in my case, it JUST recovered some 80,000 files
Let me see if I can help to explain how Recuva works:
When you save a file, your computer's Hard Disk acts just like a stone slate would. The laser etches an image into the disk that it will later read. It then adds the location of the etched image to a hidden file on the disk that most operating systems will not allow users to see (let's call this the "map" of the hard disk). When a file is deleted, the system simply opens this mapping file, and deletes the location of the image that was previously etched onto the Hard Disk. This saves both time, and the life expectancy of the Hard Disk. As you work with new files, the laser continues to etch new images onto the Hard Disk. If it comes across previous data on the Hard Disk that is not found in the mapping file, it will simply smoothen out the surface of the disk, then re-etch a new image into it, then; of course, add the location of the new image to the mapping file.
So you see, if you just delete the mapping file but never force the laser to etch ANY new images to the Hard Disk; then Recuva SHOULD be able to find that etched image. However, the very second the laser starts to re-etch an image into the location of the previous file's image, that file is impossible to recover.
When working with LIVE data (such as video or audio streams), the laser is constantly etching new images to the hard disk. Mostly likely, as you were working, the new images were being etched onto the Hard Disk where the old ones used to exist. This makes the old files impossible to recover.
This is why; just as 'SuperSport' has stated, Recuva is a "Recovery" program (hence its name) and not a "Backup" program. It can only recover files that exist with no mapping files. It cannot recover files whose image has already been etched over.