I'm going to post my thoughts on why the phone wasn't used after the last text to R. If you like the idea, that's great; if you hate the idea, that's great too. I'm not going to defend it or argue about how feasible it is.
Looking at the record of DR's texts to R, there seems to be quite a gap in the times. That tells me that both boys were probably somewhat distracted, and just sending a message when they saw fit. If DR and MR were discussing what was supposed to happen the next morning, what they'd do for Thanksgiving, etc., he may not have gotten around to responding to the last message in the 8:00 group. If he got home sometime between 8:00 and 9:00, after being up most of the night, having a rather busy day, and spending an hour or more listening to dad talk, he could have easily been sleeping by 9:27 or whatever the time was of the next text.
I didn't think it was so strange that he didn't respond, and R must not have either if he didn't send another one until the next morning. I know a lot of people have told me that one of the best things about using texts rather than voice is that you can just ignore it until you feel like responding. One of the worst things is that you sometimes forget to respond to something you maybe should have. If he was tired enough to fall asleep very quickly, he probably didn't take the time to dig out the charger, plug it in and start charging the phone. In an area with such lousy coverage there, I have no doubt that the phone would be totally dead by morning.