There is a video they made themselves which is doing the rounds on Facebook. It needs that video to go viral and on national news or papers.
Come on Daily Mail do a story use the video.
The road he was walking near is the Portway, this is a major route to get to Bristol Airport. It also has a CAZ camera just after the steep turn for Clifton, which would capture numerous cars going into the area he was last seen. People using Portway and long Ashton bypass on route to Airport etc may not be from Bristol and live far away and not heard of the missing lad. They may not have seen him themselves. However, if they have cameras on cars that might have captured his movements.