Very late reply but perhaps items that were used in an abduction, clothes or similar?
I get the feeling (gives me the willies) that one of the major suspects went there, while they were searching the other area, and the team know it. He might have gone there to remove something he threw out the window or some other piece of evidence? Hope, if he visited, he left some nice tyre track impressions. It's been wet since tho - i'm not sure what this would do. Obviously it's good if it's wet prior, but after? I think that might not be so good...