I agree that it's very possible that Karlie wandered into the desert and succumbed to the elements. I agree that dad and SM didn't handle Karlie's emotional state very well that night and IMO SM went off the rails with her YouTube videos. Still, that may not mean either of them did anything nefarious to her. But now that so much time has passed it seems to me that the most reasonable scenario is that Karlie's body is somewhere nearby in the desert. And as you say, searching such a large area is difficult. Her dad and SM may be hiding/lying about some of their actions but it doesn't necessarily have to be that they actively harmed Karlie. As much as I am wary of the dad and SM if I think the events through from a logical point of view then I cannot discount Karlie wandering into the desert due to her disorientation. And IMO a stranger happening upon Karlie on the highway and picking her up in order to harm her has incredibly low odds. The highway has traffic but it's not especially busy. IMO if they would be more truthful it might be easier to either discount that scenario or focus more upon it. The changing stories that both told only muddies the possibilities and that's not helpful in finding Karlie. All MOO.