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1/4 Mile.
RT said he last saw his wife when she was 1/4 mile from the RV.
The RV was in sight. It was right over there. Barbara could see it.
They were not wandering, aimlessly in the vast desert as their mental acuities and physical well beings were disintegrating under the hot sun.
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Have you been out there? My claim is that there are TWO trails (at least) from which she could have seen the RV (intermittently, as the Wser said - who went out there since this case started). We don't know that they were really ¼ of a mile from the RV - people are notoriously bad at guessing time and distance.
There are two trails that intersect on the way back from the boulder formation. One of those has another intersection further on, two others head to the road - one is a short distance to the road, the other is a long distance to the road.
We do not know if Barbara was suffering from heat exhaustion. I have had it (and know several other people who have had it too, have talked to or interviewed several heat stroke survivors). The symptoms are very hard to detect, especially for the sufferer.
There is no way that the RV would be visible from all the various trails and there's no way of knowing which trail Barbara would have taken (both of the ones that lead to the road would have had the RV visible intermittently; I'll be going out there in a month or two to take a video, but I'm quite certain that the opposite side of Kelbaker (where the parking lot is) is not visible (even with a tall RV) from every single point along both of those branching trails. @Sroads mentions that the RV-sized trailer that LE had was visible
most but not all of the time. If for any reason, Barbara took a true wrong turn at that intersection, and briefly headed in the wrong direction (assuming no heat exhaustion at all), when coming back to correct her mistake, she had two choices (and I'm betting that the RV was not visible from
either of those trails because I've studied a topo map and the trail intersection is at a low point in the area, that's why there is way more foliage there).
In the desert, you can tell where the lower areas are by observing evidence of water flow and by observing evidence of plant life. You can see it on Google map, but that RV would certainly have been visible from the trail they initially took
part of the time. I'll bet an entire box of donuts or bagels that it was not visible from the 4 way intersection of two trails.
Further, if Barbara could not find the key and was serious about using the restroom, she might have headed in yet another direction because, although many people are okay peeing right in full view of traffic, many of us are not, especially not in her age group (which is also my age group). It isn't just age. My daughters would seek cover and so would ever man in our family as well. Peeing at the side of the road is not something any friend I have would do either.
So she could have crossed back over the road to head for some trees near the wash or she could have walked up HH and then into the less cholla-filled area that's there.
We don't know. I will not stop considering that she could be lost out there. Especially if she had started into heat exhaustion. People do not just suddenly collapse from heat exhaustion, it's usually an hours-long process and has stages.