About the finger print thing......
Ok, I'm not entirely sure why they are fingerprinting you, and I'm almost positive you can refuse. I don't know what law allows them to do that. Of course you are probably just breathing a sigh of relieft that is all that is happening. But I don't think the police can force you to get fingerprinted if you are not being charged with a crime. However if they tell you that they are going to arrest you if you do not submit to the fingerprint because you are refusing to be fingerprinted, I would get fingerprinted and then speak with an attorney about filling a lawsuit against LAPD as well as writting to the judge overseeing LAPD due to the Rampart corruption stuff.
What they are doing with the information and fingerprint is making a prostitution contact card. If you are arrested in the future, they will use this to help prove that you have done this before. Also, they will use it if they catch you loitering again to prove you loiter often. This is the same way they document gang members, although I didn't know about the fingerprint part.
BTW, this totally underscores the need to get off the main track as quickly as possible, and get as far away from the main track as possible. It also shows the need to pay attention to anyone following you. I've only had issues come up a few times, but they all fell squarely in this advice. The only time LE has ever stopped me was on a total fluke where an UC LE just happened by where me and a girl were parked as he was going around the block for another girl. So he called in a B&W. This never ever would have happened had I been more than a block away from the main stroll. On another occasion, I had a grey van follow me through several turns. Turns out, it was 18th street back when Olympic/Alvarado was hopping and the girl I was with hadn't paid her $50 protection that night. I punched it and lost them. I have no doubt that being aware of my surroundings kept me from getting robbed and beat up that night.