Just my opinion, but to me the waving of the arms is odd. When you go looking for someone in a crowd, far away or a distance from you, you don't start waving your arms until you see the person and try to get their attention with your movements. Otherwise, you just call their name or look until you see them. That's when you throw your hands or arms up! I have no opinion about RT but I find some of his comments "off". He could have some early dementia going on which makes his comment odd to us also.
Well, the first thing we would do is honk the horn. Husband and I are, I guess, pretty experienced hikers as we actually have plans for things like this. We have to. We're both rock enthusiasts (especially him), we're both time challenged (boy does time fly when you're having fun), I tend to believe I'm impervious to heat, he is more cautious. Anyway, not only would we honk, but we actually carry a small airhorn device if we're going to be in a desolate area or off trail (we do quite a bit of off trail hiking, but in forests, not deserts).
I agree that I wouldn't wave my arms until I saw the person. Expends energy and is pointless. I would, however, quickly get my backpack down to just water and a few essentials (I would leave my stuff in a pile or throw it in the 5th wheel - I'd leave the 5th wheel unlocked, property would not be my main concern). And I'd be moving as quickly as I could back to the junction where I last saw my spouse - and I'd take a different route at that junction, as
obviously they were not on the section of trail in between the RV and that junction. If I knew for sure how long the person was gone (I now wear a watch and clock such things), I'd know approximately how far to walk (still shouting) on each trail branch. IOW, use the methods you'd use to look for a lost kid, because you don't know the mental state of the lost person.
I would also assume that my spouse might have walked eastward for a potty break (neither of us likes to pee near a road, the road there is pretty high off the desert floor and people all drive trucks). I'm sure many people have peed near the road in that place, though. I wonder if the sniffer dogs had a hard time picking out one scent to follow and I don't see how dogs could detect one person's pee from among the rest without being primed with an article of clothing. I wish I knew more about sniffer dogs.