We know cell phone reception at MR's house was spotty. It's perfectly possible that DR's phone never received the text, or that he did get it and sent a reply, but the phone was never able to transmit it.
Dear Paul,
I think you mentioned somewhere that you don't have any kids? (Forgive me if I'm wrong.) One thing that stood out for me, as a mom -- and this may sound a little stupid -- is that Dylan was polite enough to ask the other boy whether or not his grandma would mind him coming over, and seemed concerned about the early hour. Believe me, not everyone raises their children to have this kind of concern. Given that, it seems unlikely that Dylan would not let his friend know as soon as he could that plans had changed.
No cell phone "talk" reception? I can believe that, but we've been told that texting was generally not a problem, and also, at one point, we were told (I believe) that there was an area in MR's house where cell reception was actually pretty consistent -- I recall mentioning at the time that the same thing was true in my house (no, I don't know why).
So, if I go with he can't use the cell to talk, and for some reason texting is not working either, I then ask about the land line that we know existed, and the computer. People will then say maybe he didn't remember any of his friend's #s. I will respond that he could have looked up at least one of them on the internet, used the land line to make a call, asking either for the phone number of the boy he was supposed to meet, or that someone call and pass along a message for him.
I just don't see (and believe it or not, I have tried) that he couldn't get a message to _someone_, and that he wouldn't at least try, if he were able.