Seeing as Rifkin is a relatively new detective, he probably hasn't worked many cases at all. Maybe two with Bellamy before they got reassigned to Metalliká. One of the cases could have been a sting operation on a criminal group, and one of the unknown men seen meeting one of the higher criminals (One of our OC criminals) from the photos they had provided by undercover officers was never matched to a database, no name, no prints, no history nothing, everything was gone from the system.... And guess who that could be? None other than Kay.
Obviously Rifkin and Bellamy wouldn't connect two and two together for quite sometime seeing as now he's a cyborg and looks drastically different.
That's my 0.02.
Edit: Running with LeVens post from when I was writing this, it could be a rather large sting involving the whole department trying to take down a large criminal organization, or maybe it's just getting too complicated now XD