For a potential reader there must be some way to go back and see an authentic source you are referring to. I find no meaning in referring to something that only exists in a few *minds*, possibly with different interpretations for the same thing. 

One way is to *create* a source, with due permission from the mentioned CEO and then cite it. If possible and everyone attended the meeting agrees; the minutes of the conference may be edited with an addendum stating it is done so.