The so-called heliocentric “theory” is an artifice of someone who, having sour grapes for never seeing Mercury IRL, found some shitty excuse to blame his failures on the sky. /s
Serious now. I’m sceptic on the claim, that Copernicus never saw Mercury. Sure, he wouldn’t need it for his theory, but he was still interested and curious about the sky. Mercury is a pain to observe but definitively doable, and you get, like, eight good chances per year, that can be predicted with geocentric ephemerides. His best bets would be Jan-Mar (drier than other months in Poland, so there’s a bit less mist).