Also, you do realize that you still need your passport for identification for basically anything right? Living in Germany, the first thing you always hear when visiting any institution, police, hospital, pharmacy, etc. is 'Ausweis bitte!'. Without an ID, you will not be served unless you're in a life threatening emergency.
And the girls would be too afraid to go to the authorities for help, for the fear of beatings or the pimp gangs taking revenge out on their families back home, since they knew where they lived.