I always thought it could be one of three things.
1. It had to be someone who knew the parents would be going out that night and leaving the kids alone.
2. It had to be someone who knew the boys were going to the store. Did they call anyone else besides their parents and the neighbor girl (the babysitter) and just so happen to tell them they would be riding their bikes to the store.
3. With the stalker theory, maybe the perp followed Jacob's father, Jacob, and Trevor home from the hockey rink that day. Maybe not all the way to their driveway, but just enough to know what area they live in. I'm not a stalker so I don't know. Maybe he over heard Jerry talking at the rink saying that he would be leaving the kids alone that night, and leaving the perp to think that it would be the perfect time to perv around there house. Anythings possible. Or he could have followed them home another day from a grocery store, restraunt, school, etc. No telling how long Jacob could have been stalked.
I know these theories seem a little far fetched but to me nothing else makes any sense. I don't buy that idea that a perp just happened to be sitting in a ditch on a dark Sunday night hoping that a child would come strolling by. Either way you look at it, this was planned to some extent. Also it has been mentioned that Patty ordered pizza for the kids that night before they left. Did the pizza ever get delievered? So many questions, so little answers.