Let's hope he was disoriented and is holed up in someone's disused shed and not near water. And thank you for the local perspective. It seems likely that he's got to be close by because with lots of people out and about, I can't believe no one would think a naked kid riding his bike wouldn't raise some alarm.
I also think after falling off his bike,he must have hopped back on and took off quickly because he apparently didn't interact with anyone at that time. My husband is an avid cyclist. He got knocked off his bike by a Merc and although the driver kept going, other motorists stopped to check on him and someone dog walking rushed over. Husband, BTW, was fine. Ripped his trousers and he had to stop at Tesco before work and we learned why I generally pick his clothes.