I used to be a computer engineer years ago...
We used to use the term "Scratch disk" or Scratch Tape to mean any old spare disk or tape we had lying around as in, "Stick the file on a scratch disk and move it to the next machine." - for instance.
We typically never referred to a disk as being scratched but might have done so had it been inspected and seen to have had scratch marks.
I think that your message may actually say "scratch disk" meaning unknown and unidentified - that it has no reference or label written on the surface - but I could be wrong...
Good luck...
Peccavi
January 2013