I studied up on the missing people who are always disappearing at Yellowstone. They use some sort of technology. A chemical or sedative, or some new way of making people pass-out or forget. The vacationers that disappear are not immune even if having a dog alongside them. Whatever technology is used doesn't even leave a scent for the search-and-rescue dogs to find. So they have a way of masking your scent or making you go away fast. Best chances of not going missing goes to those who have a lookout nearby, or travel in able-bodied groups. But vast majority of the disappearances from around the u.s. come from 6 or 7 places, Yellowstone being one of those places. Mostly if alone after separating from a group.