If they had a conversation, and nothing was recorded, for any reason, then it's not possible to use Jeff and Susan's meeting as data. Researchers must have physical and strong data to create a proper answer for what they are researching. In this case, maybe they will use Jeff and Susan trough another way, such as their personality or their past, or how they meet themselves. But the conversation it's not possible to be used, because, through the eyes of History, this conversation doesn't exist, because it was not recorded.
