Hi, hon! Well, you're right - I agree! One would think, huh??
I am always surprised when I hear things like this.
I think it's sad when someone gets in trouble, regardless of who it is. Most of the time, anyway.. But,
I'll tell you why that happened: LE officers are not always privy to the information that the targeted crimes unit, is. The officer in question was likely in another dept., or on another task force in their dept., or another jurisdiction, although all have reciprocity. They'd have to submit a request to know certain info., depending on the jurisdiction, and with good reason. That was what I was told by someone I know quite well who is "one of the good guys," who helps us ladies stay safe.  
Organizations such as MADET (Multi Agency Drug Enforcement Team) focuses their efforts on vice crimes such as drugs, prostitution and what falls under organized crimes such as racketeering and so on. When they perform a sting, they don't announce it. So NO ONE is impervious to the sting of the bee.