So, going with what we have....
We know that the following are missing and presumably with Dylan: backpack, phone, phone charger, fishing pole.
I can see Dylan taking a fishing pole, backpack, and phone to go fishing. But NOT a phone charger. That, for me, eliminates the possibility of a voluntary fishing trip.
I can see Dylan taking a backpack, phone, and phone charger to hitch a ride back to his hometown or back to mom's. But NOT a fishing pole. That, for me, eliminates the possibility of a voluntary trip back home.
These things just do not go together and SHOULD that fishing pole that was found on the dam turn out to be Dylan's, I just cannot believe that he would blow off plans with his friends without contacting them and go fishing, bringing his phone charger along just for the hell of it.
The evidence, for me, points to something more sinister. Someone was too sloppy in trying to get rid of evidence and set up an alibi. JMO.