I mean.. if I were him I'd be doing my best to not let the CIA and NSA know where my Moscow apartment was located...
Kim Philby lived in Moscow for decades, I don't think he went to any great lengths to dodge his former MI6 colleagues. I would bet the US government knows exactly where Snowden is living. It won't be that hard: he'll be surrounded by secret police keeping tabs.
Yeah, it's not like CIA agents would kidnap him or something. Would never happen, right?
While I'm sure the they would love to get their hands on him, pulling off a kidnapping from under the noses of several Russian intelligence agencies in the heart of their domain seems like a stretch, even for the CIA.