Strange "Handover" Ceremony at MACV Headquarters, Saigon, Vietnam?

I recall reading something about a very strange happening, at the end of the Vietnam War. When the USA formally ended its military role in Vietnam (1973?), a very strange ceremony took place at the Military Assistance Commond Building, in Saigon. The assembled crowd (reporters, Vietnamese government peple, etc.) were sitting in an auditorium, an nobody was at the speaker’s podium-instead, a disembodied voive made a speech, announcing the end of the US military effort.
Presumably, this was because the circumstances were so humiliating-nobody (least of all a general) wanted to be seen as the last guy to put out the lights.
Does anybody have a good account of the rather bizarre final ceremony? I’ve been wondering for years.