I have notched about 100 jaunts into JTNP and its backcountry over the past decade. I've long since lost track of the exact count.
Against that backdrop and my knowledge of walking in the Park and its terrain, a loop as described would be near impossible in practice, though it definitely would look good on paper to someone who loved the area but didn't visit it often, a description I believe fitted Bill. That is a lot of miles to walk after a late start and the terrain is not flat. It is tiring to dip into and out of dozens of little washes, slog through sandy areas, and the like.
If you park at Juniper Flats, you're in one of the more densely vegetated portions of JTNP. It may not look that way from satellite view but those Joshua Trees give the impression of crowding around. That makes one naturally want to follow a trail. Juniper Flats to Quail Mountain is one obvious route from that parking area. The CRHT does head out towards Ryan Mountain from there as well but is a little less obvious.
Geology Tour Road is a hard-packed dirt road in its upper reaches. The CRHT is a pleasant walk heading towards GTR, but once you reach GTR it is an unappealing slog up that road, to a busy part of the Park. To reach Queen Mine / Lucky Boy, you have a couple miles up a well-graded dirt road, followed by a fairly short trail. All in all not a particularly appealing walk. Now, it is possible that Bill chose not to drive a dirt road in his rental and so thought he'd walk in to Queen Mine. Instead of taking such a huge walk to get there he could have parked in pull-outs close to the dirt road or in the parking lot for GTR just across the main drag. ( I've done this myself before when the road to Queen Mine was closed due to flooding ).
How about walking from Queen Mine to Barker Dam? As it turns out I've done that, too. There are dirt roads, or you can go overland. I've done both. ( The dirt road to the Queen Mine parking lot is better graded than the ones across the valley, which is why I parked there and then walked. This was back in my 2WD days ) The dirt roads can be sandy, making them tiring to walk on, and overland means a lot more of those little micro-scrambles that can wear you out. But it is doable, if a rather tiring walk. None of this walking happens in the remote backcountry, by the way. That part of the Park doesn't "feel" remote at all. You're right there in the bustle, though in summer 2010 JTNP was a lot less busy than it is now.
Finally, if you do reach Barker Dam from that walk, the big parking lot is can't-miss, and the trail to Barker Dam is well-marked and well-traveled. You cannot easily stray into the Wonderland from this trail because of how the topography is. ( The Park prefers trails in areas where tourists can be well-confined. Trails like the Maze Loop where Orbeso was lost are more recent, more open additions. Barker Dam is about as close to Disney World as JTNP gets! ) There is a dicey bit once you're west past the dam where the terrain opens out into rock piles so you could stray a bit, but the trail is well marked and that area is always packed with climbers and the like - not really somewhere you can be lost for 9 years.
Another thing about Barker Dam - it doesn't always have water in it. Also, the Park prohibits visitors from gathering water anywhere in the Park - Barker Dam, Smith Water Canyon ... it is all off limits. A visitor planning a hike and reading some information should discover this.
Incidentally, I've been all over the Wonderland of Rocks. It is often described as being maze-like, but it isn't that bad. ( Disclaimer: if you are inexperienced in backcountry overland travel or have a bad sense of direction it could be very bad indeed ) And it isn't deserted, either. Every wash has footprints, even way in deep where you have to scramble to reach. So while it wasn't searched for Bill specifically, that I know of, it is still well-traveled. Lots of rock climbers and explorers go through there every year.
As for why my money is still on the expected search area, let's turn to Paul Miller's case.
https://kesq.com/news/2019/12/23/family ... onal-park/Robinson told CTV News the family passed within 21 yards of the location where the remains were later discovered during one of their multiple ground searches.
It really is that easy to walk practically right by someone and not see them in JT's back country. That's why I still think Bill is somewhere in one of the many, many tiny unsearched areas between Quail Mountain and Smith Water Canyon. You only need two or three yards to be hidden on the other side of a rock, or half-covered on the far side of a juniper or creosote.