Who is to say native americans was not inspired by God as well. It is something none of us can prove one way or the other.
Because they don't know God, they don't recognize God, they have no myths concerning a God that is anything like the Judeo-Christian God, they have no stories about some sort of soap-recipe from the sky, they have nothing of the sort. They just have their extensive knowledge of plants and herbs and their medicinal properties acquired through thousands of years of living in the bush.
I cannot seriously believe that you do not find that a more plausible explanation - that the Native Americans came by their soap recipe the same as we discover anything else (without divine intervention) - than a magic soap recipe being beamed down from the clouds into Numbers 19. Because people have come up with plenty of things without God's help. This is evident. And if that is so - and it is - then that makes the source of the soap recipe in Numbers 19 that much more improbable.
You haven't explained how you know this soap recipe came from God. And whether you do or not, it doesn't particularly matter, because we're far off on a digression anyway. PureX's point was that faith healing forms the basis of modern medicine (or at the very least many practices are derived from faith healing). An ancient soap recipe isn't faith healing nor is it the basis of modern medicine.