It's unclear to me whether the phone calls came in while he was even on the mountain. This may've all been a big misunderstanding. Like, I don't know how they track hikers, but it sounds like they were looking for the guy and eventually found that while he had gotten a bit turned around and stayed out longer than intended, he was chilling at home while they were still searching for him.
So yeah, I think the lesson here isn't "pick up your phone if you were recently hiking, because it might be park services thinking you're lost," it's "park services, leave a voice mail/send a text, and maybe get yourself listed by name in Caller ID: some people don't just pick up unknown numbers."