So many angles to this, but can't get away from the fact they had a lot of cash with them and that's the clincher IMO. No one really buys property with cash, or even likes to drive around with it, so surely it was for drugs, and this was meth country. The property purchase was a cover story for the money just in case they were searched and why they were in the area. They might even have considered to get a property for real as a cover for future drug runs, who knows, but it's simply not realistic to give up a nice lake side house to live in a steel container shell in the middle of the woods with a kid.
Half of the cash from an insurance settlement was in a briefcase, and the rest was under the seat in the car. The perps didn't forget about the cash in the car, they just didn't know it was there, but they did get the half that was in the briefcase.
The Jamisons, talking to locals made sure they were told the story about their intent to buy land so no one would get suspicious that they would be hanging around the area for days. They took photos of different well site signs as one of those would be the meeting place. And hanging around they were. When they finally found the well site meeting place (communications with dealers by voice mail?), they were just loitering there, painting graffiti on abandoned wrecks and going for small hikes when Madyson got too restless. The photo of her on one of their small hikes showed she was well fed up of it, and the nervousness of the parents had surely rubbed off on her so she knew something was up and wanted to go home. They were obviously waiting for something, and it was for a deal.
Soon enough it came, and they were told to leave their phones in the car so as not to be tracked and come with the dealers. They did that, locked their truck, and got in the dealers' vehicle, probably carrying the briefcase with the money and Sherilynn's gun. The dealers soon realized these people could not to be trusted an inch bringing a kid with them - or never planned to in the first place - and with a $32K bonus decided to waste them. They therefore made up a story that the stash or lab was somewhere in the woods just in here (in the most remote and least visited place not even searchers would find, proving their local knowledge), and after a little hike forced them to lie down on their stomachs and slit their throats. They then covered them up so they wouldn't be found in a hurry which obviously worked very well.
