Perhaps it was his parents?
Perhaps they had been out looking for him and found him riding a bicycle which wasn't his somewhere beyond a boundary they had set?
There's no harm in being vigilant but no need to start criticising anyone just yet...
I remember watching a programme on TV. I think it was Wire in the Blood where a girl was snatched off the street and later a girls matching her di scripting was found dead.
It turned out that the parent 'snatched his daughter as she was bunking off school and the dead girl was an unrelated event.
However in this case they have the van details but the owner has been ruled out. Cloning of numberplates perhaps or something else going on?
If the child hasn't been reported missing I can only imagine that his parents know who he's with. If that's the case, they really ought to inform the police.
Possible scanario - traveller kid on stolen bike strayed too far from home so rounded up by family/friends. Left the bike behind. Family wouldn`t tell the police that it`s their kid because travellers won`t have any dealings with the police and the bike was stolen so don`t want to be connected with it (there have been a spate of bikes stolen from garages by travellers round here over the last couple of weeks so it`s not impossible)