I see 
ok so how about how the child is kidnapped eg. If they were taken by car perhaps there are tire tracks left behind which could give a clue as to which direction they went and what type of tires to look for.
If they were taken by foot then maybe look for some footprints which could later be analysed to match footwear. Mayber thw kidnapper leaves something behind eg a hat? They could find a certain brand of hat thwy wore and then go to the shop to ask questions on if they could recognise who brought it.