Several things might erase it. Try at your own risk. I doubt a magnet will have any effect. There may be a small battery that can be removed for a few minutes. There also might be a large value capacitor (several Farads!) that can be shorted (through a resistor) for a while to reset the circuit. Static electricity may work, but will probably damage other parts of the circuit. You might just want to contact the manufacturer as there is probably a very simple way to do this.
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