The way I see it Kirkwood police dropped the ball several times while Shawn was right under their noses. Devlin was social with them because of his public job at a local eatery and this helped Devlin in the long run.
i agree that many dropped the ball recovering Shawn and I think the reason why is most police assume that kids missing for years is a kid not coming home and not worth the time to keep looking at every situation when presented with eyes wide open. However, I think some of the people living in Devlin's apt. building may not be so honest.
I see it that way also.