So I'm gonna play my bullshit card, esp. if there were real diplomats in the room negotiating with him face to face.
Awwwww, you're no fun. Where's your sense of adventure? Your sense of conspiracy? Remember it took days for the world to learn of Stalin's death back in 1954. And how about the string of Chinese leaders who have died, starting with Mao? In an age of instant communications is took a while for their passings to become common knowledge.
So who's to say some Star Chamber in North Korea, reputedly the world's "most closed society," couldn't pull off such a ruse and keep that ball rolling for years?
And as for in-person negotiations, one pot-bellied, brush-cut, moon-faced, splay-footed dude with halitosis (OK, I'm just guessing, here) looks pretty much the same as another.