We could try to analyze the tremendous amount of visual data collected - photographs, video, CCTV footage. Discern abnormalities in appearance, clothes, possibl

We could try to analyze the tremendous amount of visual data collected - photographs, video, CCTV footage. Discern abnormalities in appearance, clothes, possible gadgets used, movement, behavior. Given the abundance of recording devices today, chances are they got caught on tape or had their picture taken somewhere. Of course there's always a possibility of false positives (e.g. Lady Gaga), but I think it may worth a shot :)