Just wanted to add a few thoughts as I've explored this exact area.
I was initially thrown off by the media reports that they were 20 miles north of I-40, as there aren't really any campsites there and nothing to explore. So the info that it was actually near Hidden Hills (about 9 miles north of I-40) makes a lot more sense. There are a bunch of really great boondocking sites just past Granite Pass, off of dirt roads to the west of Kelbaker rd. I would bet that's where their trailer was, and the "highway" she had to cross to get back to the camper was Kelbaker rd. Kelbaker rd. is not very busy at all, so the likelihood of encountering a car would be small, but also if you did, there likely wouldn't be anyone else around to see you. Also, yes, camping in the desert might seem crazy to a lot of you, but to a desert rat it's nothing unusual, and Granite Pass is a great area to choose because it's at about 4000 ft elevation. And the campsites are nestled into the mountains such that the sun sets behind them pretty early, making them nice and cool (in the desert it cools off pretty quickly in the shade).
Abduction does seem farfetched to me at first thought, as it seems more likely to me that she got lost on her way back, or possibly while looking for shade to cool off on her way. That area with the campsites is nestled up against the Granite Mountains, which are literally just piles of boulders strewn everywhere, like a maze of rocks, so it would be quite easy to get lost. The campsites are set back quite a ways from the road, and though one could just walk down the dirt roads towards them, in that heat I know I would be tempted to take a shortcut across the boulders.
BUT that said, I could also see another possibility : she reached Kelbaker rd, where a car was passing. Maybe that person stopped and offered her a ride back to her camper, which would be tempting to anyone in that heat, especially since as I said, the campsites are still quite a ways from the road (the closest site is about 1/2 mile). In that case, abduction becomes a possibility. I don't know Barbara personally at all, but I've also found that older people tend to be more trusting of strangers than I would be. I know I (30-something woman) would NEVER accept a ride, even from a seemingly kind person, but I bet my 60-something mom would. It's scary to think about.