I know one fishing area has been searched, but are there other lakes within walking distance of his dad's house?
Just thinking that if Dylan had had breakfast and got bored of watching tv, he may have decided to kill the couple of hours before dad got back by going fishing, if it was only a short walk away. Grabs backpack as he hadn't bothered to unpack it yet, so takes the lot including phone. No note needed for dad, as Dylan planned to be back at the house by 11am.
Then something happened there .... either he fell in (explains why phone has never pinged since then), or he encountered someone there, or on the way to the lake or on the way back.
However, if that did happen, I still would think he'd have text his friends to let them know he was arriving later than the 6.30am planned. Unless he wasn't aware his phone was dead until he got there, and couldn't charge it.
I still can't decide what I think happened - the phone circumstantial evidence points to something happening around 8pm the previous evening, but everything else seems to confirm that Dylan was up and well by the following morning (breakfast bowl, tv on kids channel etc) ...... unless LE are just letting people believe that.