Of course I have no real idea what kind of hunter BM is -- I am only going on the word of a relative. BM could be BSing about that as much as he BSes about everything else. I do think he, SM and the kids were somewhat outdoorsy (skiing, biking) if you go by their social media. But who knows? Maybe they skied one day of 2 weeks in Vail, and then spent the rest of the time shopping and eating out.
However, I have been in the Salida area several times and used to live in Colorado and Montana -- I've been in areas in which you could lose a mammoth carcass. And I'm not a hardcore hiker, biker, or camper. I have never hiked and tented overnight in any back country. Even for me, it would be easy to find a place where she would never be found. Look at all those back-country hikers in the national parks -- they disappear and years later someone finds a bone or a weathered backpack, and that's after rangers have searched for weeks. SM is in the same position.