Well Dan, this is obvious.
Oswald was in the process of flight from the scene of his crime and while coming down the stairs Oswald heard Truly shouting up the adjacent elevator shaft to release the elevator, so Oswald made a beeline for neutral explainable territory, the 2nd floor lunchroom.
Then after being confronted by Truly and Baker in the lunchroom and then fortunately being left alone a Oswald realized that he would have had to have a reason for why he was seen entering the lunchroom hence his coke purchase.
Mr. BELIN. You might put a "B" on Exhibit 362 by the elevator for "button."
Mr. TRULY. That is right on this surface. There is a little button. I pressed the button and the elevator didn't move.
I called upstairs , "Turn loose the elevator."
Mr. BELIN. When you say call up, in what kind of a voice did you call?
Mr. TRULY. Real loud. I suppose in an excited voice. But loud enough that anyone could have heard me if they had not been over stacking or making a little noise. But I rang the bell and pushed this button.
JohnM
We're definitely going to have to disagree over what's obvious and what's not.
The fleeing assassin hears his boss shouting up the elevator shaft and feels the need to find a "neutral explainable territory"??
Why does it need to be "explainable" if it's Truly?
Let's say he hears footsteps thundering up the wooden staircase as he gets on the 2nd floor and decides to duck in through the vestibule door just in case. To his left is the lunchroom, to his right is a door leading to a corridor that can take him to the stairs down to the front lobby (or he can go through the office space).
One way is freedom and the other is a dead end. So he chooses the dead end? Not convinced. Surely he's either a fleeing assassin or he's not.
Any reasonable person would automatically assume that a fleeing assassin would opt to make his way to the entrance of the building. I think it's obvious that, because you view Oswald as the assassin, you have to come up with some kind of explanation for his presence in the 2nd floor lunchroom when, in fact, the unlikeliness of the incident points to an explanation other than Oswald coming down from the 6th.
The best thing that can be said is that it's not impossible that Oswald decided to duck into the lunchroom to get away from approaching footsteps then decided to get a Coke as some kind of cover. It's just really unlikely.