Long before the mammoths were around, there used to be rhinoceros living in the Siberian region. Hence, sometimes, the mammoth ivory hunters would excavate rhinoceros horns by chance.
As the years went by, the rhinoceros' horns would turn into something that was between fossil and bone. It had no ornamental value and carried a faint smell. By external appearance, it looked like it had been carved out of wood.
However, it was in fact very valuable. Its unit price was much higher than that of ivory. In Southeast Asia countries like Myanmar, Laos, Thailand and other places, the rhinoceros horn was used as folk medicine, and its price was comparable to gold.
One would need more luck to be able to find rhino horns than mammoth ivory. There was not much use for experience. That was because the horns were simply too rare and every time someone found one, it had been purely thanks to luck.