The write up referred to the poster going under the nickname "Merkle923". Most likely that is Keith Olbermann.
Regarding Conlon leaving the game or missing the moment. How will we ever know what really happened? Maybe he did capture the moment. As the melee erupted, maybe someone bumped him and broke the fragile glass plate negative. Maybe he got mugged but angry fans who were attempting to destroy the evidence.
Maybe he captured the moment and the negative still exists in the collection. If he did miss it, I forgive him. I think he can be given a free pass given all of the other great shots he didn't miss. If Conlon did miss it, then all of the other photogs in attendance missed it as well. Rhys probably has the most correct scenario.