Idk about that. Magnets have been known for a very long time, and if you know that magnets always point north and the world is a sphere (which was known in classical antiquity.) it's pretty easy to put the two together and know that there must be a magnetic pole.

I still think it's wild that some guy worked out the circumference of the earth thousands of years ago using two sticks and some trigonometry. I think he was right to within a few hundred miles.