Those guys can be crooked too
Don't believe me just ask some former choirboys.
First off, do you have a way to actually decrypt the data if you find the key sector? E.G. Do you have PC-3000? If not it may not matter much. The magic sector is hidden in an HPA near the end of the drive (by replacing the PCB it'll now be open). Just search backward from the end of the drive for the letters "WD". You'll find a sector which starts with those letters and contains the encryption key.