When prostitutes go missing police should see if drug dealers in the area are selling Devil's Breath (Scopolamine). It is used to rob, rape, and murder people. If there are dealers selling it in the area, they should try to find out who the repeat customers are that are buying it from the dealers. There's probably also online black market ways of getting the drug too. It's available in North America, not just South America and Central America. I would wager that a lot of law enforcement agencies don't know that this drug even exists.
This drug gives the perpetrator complete control over the conscious, but very drugged victim. However, looking at the victim you would never know cause they don't look or act drugged. The perp can make the victim do things they would never normally do like leave their phones behind, tell a driver/security they don't need them, go places they normally wouldn't, not follow security protocols, etc.. When the drug wears off the victim won't remember a thing.
[video=youtube;ToQ8PWYnu04]http://www.youtube.com/watch?v=ToQ8PWYnu04[/video]