Just going to post some information here about magnets and electronic components folks. You can look at more stuff on this with a web search. But like I said before: it is highly unlikely that the magnet caused this problem.
From "The Top Eight Computer Myths""8: Magnetic mayhem
One of the basic tips in every computers-for-idiots book is to keep your floppy disks and other magnetic media away from magnetic fields, lest your data be wiped.
Magnetic fields can, indeed, eat data, but the usual suspects aren't generally the problem.
Every ordinary cone-type speaker driver has a large permanent magnet on its back, to give its electromagnetic voice coil something to push against. "Shielded" speakers neutralize the magnetic field with another, opposed magnet glued to the voice coil one, which reduces the driver's efficiency but does the job. An unshielded speaker's magnetic field is clearly apparent if you put it too close to your monitor - the image will distort and change color, and in extreme cases stay that way, despite the monitor's built in "degaussing" circuit, until someone makes magic passes over the device with a degaussing wand.
But putting a floppy disk on top of an unshielded speaker won't hurt the data on the disk at all. This is partly because a change in magnetic field strength is helpful in erasing disks when the field is more or less powerful enough to flip the bits, but mainly because the magnet on the back of a speaker may only barely be strong enough to erase a floppy even if you put the disk right on top of the bare driver. A rapidly oscillating magnetic field of greater strength is much more dangerous than the weaker, static one from a simple permanent magnet inside a box.
A old fashioned bell-ringer telephone contains a pulsing electromagnet that moves its bell-clapper, and a disk leant up against it is likely to be a goner in short order. The above mentioned monitor degauss circuit may zap disks left atop the screen pretty well, too, and some printers, especially older dot matrix models, contain quite large and poorly magnetically shielded motors.
Essentially, any electronic device with moving parts may be able to zot your floppies, tapes and Zip disks. It doesn't have to be able to pick up a paper clip to be dangerous."
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The Top Eight Computer Myths!