Bill,
Listings expire from CL after seven days. That's why you didn't see the 45 year old Maya.
The cops can indeed use nudity in ads, but they wouldn't post an officer's nude picture. I'm not sure they'd post any real picture of an officer; that seems like a serious safety and security breach for them. Instead, it'd be strange if they couldn't find a picture from anywhere that didn't look enough like the decoy to work with, at least as long as it took to get the bust done. A lot of providers post fake pictures anyway.
Bear in mind that the elements of soliciting are an offer of a fee for sex, so a decoy would steer the conversation in that direction, trying to get you to say the incriminating things. Real providers are cagier and many won't discuss much over the phone for that reason.
Even if it's legally permissible, I don't believe officers do disrobe in front of marks. As Slinky has pointed out elsewhere, there would be public relations repercussions if the police did something like that. He's said that there are things that are against departmental policy even if they're legal. I agree with that.
Keep your head about this kind of thing. Don't live in fear, but use your big head too. If you're afraid of everything you won't enjoy the hobby and you'll miss the genuine danger signs. Remember soliciting is a misdemeanor, not a felony, and the main weapon the cops use is fear. Fear of exposure, mostly. That's why they publicize as much as they can. That's why every time they bust a spa they found "customer records" and "videotapes" that they're "reviewing." You never hear any more about it, but the purpose has been achieved.
As for the 45 year old Maya, what should you do? Don't call her. There's plenty of other choices, so there's no point in taking even a small chance.