[Nordic]

Actually static magnets (fields) are the most disruptive for magnetically stored media, so we didn't have the disk plugged in - the magnet and disk were "not moving". Actually the data stored on disk is less prone to damage when it's running because of the reason you mentioned!
EMI might disrupt data communication between disk and motherboard but you need the correct amplitude and frequency to cause transmission errors.

Heh, I better talk to the electrical engineer at work who got the idea, in case my claims aren't correct.