No way for him to know.
The last time hasn't happened yet.
My intuition tells me that his notable absence in the situation room the night of the Benghazi slaughter is because he was blown away on dope upstairs in their living quarters.
If Trump had brought a dope sniffing dog into the presidential quarters the day after the Obamas moved out the dog would probably have overdosed on just what Barack spilled over the years.
The fact that Nobama still has not disclosed his actions that night speaks loads.