There are ways to find silver without the wishbone, but it's a painfully slow trial/error.
While in the upper mountains, you wack the Stagbreaker on the ground. If you have small gray zeros it means you've wacked something very hard under your feet. It might be silver. Or not. I tried that method but it was too slow. And I only found silver once. And it took hours. (I was lazy and didn't want to battle the Bonemass, which I did finally).