You can't necessarily compare relatively recent human bones to the bighorn sheep bones in that photo. I've been literally almost standing on a 3-year-old (from date of death) pelvis and it took me like 5 minutes to spot it--the only reason I saw it was that my dog was alerting like crazy so I knew there was something in the area. My foot was like 6 inches away from it. They start out stained and especially if they're partially buried it can be really difficult to recognize them as what they are.

Also I'm not entirely sure where you're getting that the bones aren't usually scattered. After 5 years of desert rains and predation I'd expect scattering. We often only recover partial bodies after a much shorter period of time (like months) in very similar ecosystems to JTNP (never been involved with a search there yet, but most of my searches are in similar deserts and I've hiked and trained in JTNP pretty extensively). There aren't a ton of predators/scavengers there but there's a decent coyote population, plus if the body fell on a steep hill or in an arroyo or canyon, flash flooding will tear it apart.

Decomp is weird. I live in the desert and I used to ride about once a week by a cow that died during calving. Nothing ever touched her and she was mummified. I saw her for 3 years and she was still pretty intact.

OTOH, I spotted another recently dead cow in the same area, less than a mile away as the crow flies, and used to ride out and check on it. It was significantly preyed upon within a few weeks, and scattered within a few months. After the rainy season hit, it was pretty much gone.

For that matter, on that same case where I was almost standing on the pelvis, there was a mostly intact sheep skeleton in the vicinity that had been there since before the victim had died (it was noted on the initial police report). Yet his body was so scattered that even with dogs we only were able to locate a small portion of it.

So yeah, it's hard to say. And while you're right that his gear would probably still be intact, if it was in a wash and affected by flooding during the rainy season, it could easily be buried or carried out of the search area.