In ancient times with no light pollution they could probably see and track meteorites falling. And it could have been easier to access to get those metals than mining.
So perhaps they mostly just picked weird rocks up off the ground, as the Inuit did? When you spend time outside with the herds you probably notice unusual wrongs.
Not exactly the same, but I’ve seen video of meteorite collecting on the Antarctic ice sheet near the South Pole and they just fan out in a big line and walk across the ice picking up meteorites.