Even if it was only 15 minutes, I agree that he could have covered quite a bit of territory in that time ... especially with the sunset not occurring until about 4 hours later.sounds like he was unsupervised for about 15 mins so thats quite a long time to wander
They have now called off the search (which has been vast) and hope of finding him alive. I would imagine that some people there would be still keeping a lookout for him.
With the information that has been forthcoming from his family and the public, and the checking/revealing of people's movements in the area, hopefully the Police are now narrowing down to who might be involved in his disappearance.