You got grafted. As we say in the old town. Fail to see how this is the police's fault though.
You just seem to be projecting your bitterness on the two plods that processed you. You should have accepted it as a life lesson and moved on.
I'm a mug, live and learn, luckily it was only £200 which was spent anyway and the only thing I missed was a fuck. My life lesson, learned and shared, is that pro$$ies, however you find them, are plentiful, be sure to fuck them on your terms or move on.
As for the plod, it's the same old shit, women are always the victim and while that is the default position they can get away with robbing punters. How often things like this go on I have no idea, a hidden crime, very few punters would admit to being robbed and even fewer would report it.
My advice, don't get stung. After being stung report it here instead of to the old bill.