I deleted a whole bunch of files on a external 500Gb hard drive. Never saved any other files to the hard drive afterward, NEVER. Yet I am doing a file recovery on the drive now and Recuva is showing a bunch of those deleted files as unrecoverable. That cannot be possible!
The files it says have overwritten the ones I am after, were there a long time ago!
I am very angry!
You could always try other file recovery tools, if needing your files back is critical don't get locked into using just one program to recover them.
As for them showing up as unrecoverable:
Even if nothing is ever touched by the user on a drive after storing files on it that doesn't mean that operating systems aren't doing something in the background which can make recovery difficult and what Windows does can make recovery an issue.
It's important to always have at least 3 backups of important files, with 1 copy being off-sight such as being left at a relatives house or in a safety deposit box, etc.
Is the drive formatted as FAT32?
How did you delete the files? Was it a secure delete by any chance?
Despite Recuva saying that they are unrecoverable you could still try recovering them.
(For example Augeas asks about FAT32 because the way a deleted file is marked as being deleted in FAT32 means that it will show as unrecoverable, but can sometimes still be recovered anyway).
Or try a deep scan with Recuva and see what results that gives.
Or as already suggested try using a different recovery tool.
More details of the drive type/make/model and what fiesystem it is formatted with might help us give other suggestions.