Memo

I recently found a note that I had made to myself some years ago following a discussion with a colleague. I wrote the note because, at the time, I was so surprised at her response. I had raised something with her - something about which I have absolutely no recollection. (That probably means that it had something to do with 'admin'. This is something I detest but something in which she delights.) Rather than make a note of the matter I had raised (which I am sure was pretty minor and was not in need of any official documentation), she asked me to send her a memo. Send a memo!? There I was, standing there having delivered the communication in person. Why did she want me, when I had returned to my office, to send a printed memo back to where I had just been, containing the information that had just been imparted in person?
All that must have happened over ten years ago. Having re-lived that episode in writing the above, I still don't get it.