Every now and then I remember the young reporter who tried to demonstrate her knowledge of Latin singular and plural nouns by writing, "When the candidate landed at the airport, there was only one medium at his news conference." For my part, I still correct student papers that treat the media as singular.
Nevertheless, the singular noun still has meaning and significance beyond fortune-telling. Nations often conduct their diplomacy through special people, especially when the normal channels like ambassadors are unavailable. The United States uses special "U.S. interests" sections of friendly embassies to maintain low level contacts with the Cuban and Iranian governments, for example.
Now we learn, via Foreign Policy's well-connected Josh Rogin, that a North Korean diplomat at the UN in New York alerted U.S. officials in advance of the DPRK's latest nuclear test. Reportedly this official has been a regular source of contact and information sharing that otherwise could not take place. It's even encouraging that North Korea would notify the American government, although the detonation itself is a worrisome sign that international sanctions are failing. Encouraging because nations need channels of communication to limit errors and miscalculations that can lead to avoidable military responses. That's why one of the first US-Soviet agreements after the terrifying Cuban missile crisis was to establish a hotline between the leaders. Short of that, it's good when there are cold lines like the one from NYC.