Imo there can't be much done about it really.

I knew someone in the past irl who actually sold women and young girls against their will for literally a few decades. He never got arrested for that even though he served 15 years in jail for other reasons.
What I'm saying is that it isn't easy to get into that entire slave/prostitute thing as a cop, and vice versa out of it too as a woman.

Don't really think that its preventable in huge societies and cities, also pretty sure things like selling women or enslaving people in general was always a thing in the history of humanity, so rip.