Again, this is horribly sad. There are obviously tonnes of posts indicating the belief that the parents had something to do with it, along with all of the inconsistencies.
IF that is the case, my feeling is he won't be in the campground area at all.
For example if it was an accidental death - they slept all three in the truck and something very sad accidentally happened in the night and they woke up to that and panicked, then you would look at the area in Leadore, near roads, that they got lost (how?) after or before visiting the store.
He wasn't being watched properly and there were bodies of water around. If he had left grandpa and tried to get back to the parents maybe something awful happened, either way, to me the weird trip to Leadore really sticks out, as does the going half a mile down the road to get signal, the getting lost really sticks out, they had only gone to go to the shop, is that right? So to get lost is odd. There are a limited number of roads around there and a limited number of roads that are not within sight of things and he would be near to the road. Well, that's how I'd look if I believed that was what happened. It would be heart-wrenchingly sad if he did wander off and got lost somewhere at the campsite.
I don't like this story because of reading that the parents left the campsite the next day, if that is accurate I just can't imagine any reasonable scenario where your child goes missing and you know the exact spot and you have camping equipment and you don't stay there for days? I mean I would keep looking for weeks personally. It's your child.