Erasing scent in a tracking situation.

Okay. So I created a problem. I can solve it using paranormal means if I want because those elements are in the book but I want to do it in a more survivalist way. The crime Samantha is solving in Jackson WY is that 3 girls have gone missing. Each on different days doing different things but in the same general area around a lake near town. Part of why Sam was called to investigate was because the tracking dogs can track the scent for so long and then it is as if the children vanish into thin air. No more scent. No clothes recovered. I can get creative and go all paranormal if I want. After all Sam is a shapeshifter and one family has a father who is psychic. Out there is acceptable in my world. BUT I really do want to have survival stuff in the book. So thoughts? Ideas? All girls will be found alive at the end but captive.