A question for the LDS members only?

I was wondering about the battle of orah? This battle was huge right? Millions of people in this battle? Why has absolutly nothing of any kind (evidence) been found? I can take you to places in Nevada where there where native american pow wow's where only maybe there where thousands of people who attended. There is evidence for 5 square miles, you could literally pick up gunnie sacks full of evidence. And why did every single person die and disappear?