Not necessarily. Depends on how powerful of a magnetic field it's been exposed to and/or duration of exposure. Repeated/prolonged exposures to relatively weak magnetic fields can add up to the same effect as a single brief exposure to a strong field. I forget which channel (LI Watch maybe?), but I've seen a video demonstrating magnetism and watches and the presenter exposed a watch to a strong magnet for a few seconds and then put it back on the timegrapher and it had sped up only by ~20 spd (and subsequent de-mag resulted in it returning very close to where it was at when they started). Reduced exposure could potentially result in a watch that was running ~+1 spd to speed up to ~+12 spd. Not outside of the realm of possibility.Second, it does not sound like it was magnetized. As understand that, if it were magnetized, the swing would be minutes per hour, not seconds per day.