There could have been a confidential meeting where demonstrations were made by PowerPoint or confidential document information that was retrieved after the meeting - view only - pending required NDA protections to move forward. In that instance, there may not be much on the plan. I do however agree that if someone resigned on the subject there should be emails and also emails setting up any meetings. I doubt there will be much on the substance of the proposed development, however.
What I do know, however, is that now the president is in a pickle and owes some explanation. Maybe there is one. Not listening is not an acceptable explanation.