They have searched with trackers, cowboys on horseback, dogs (including Ben's bother with Ben's dog, drones, helicopters, volunteers and SAR. If he did ride up there and somehow become separated from his horse, then at that point he's on foot and not able to cover nearly the same distance. Photos from there show open areas and snow covered areas as well, fairly easy to see what's on the ground. He'd have to be really well concealed in some type of shelter to not be seen. And then, if he was able to make it to a shelter, he should be able to signal for help. JMO