Let's make sure you understand. This is on an EXTERNAL USB drive; not a system drive, etc.
Have several dirs on the disk dir A, Dir B, etc with files on them. Do a backup of many files to a new dir C.
Accidentally delete dir C. Run recuva IMMEDIATELY before any new data can be over written.
Recuva shows shows a few unrecoverable files that were over written from files in Dir A and/or Dir B.
These two directories were on the drive previous to the accidental delete of dir c and NOTHING was added to them
Again I wrote NOTHING to the drive (and I doubt Windows did either) between the time I accidentally deleted dir C and ran Recuva.
How two existing files can be moved ON TOP of freshly deleted files is what I don't understand.