Apparently he knew.
"Well, speaking with all possible respect, it seems to have affected my mother's brain.

I was already with the royal army and of course there could be no question of regular postal communications with France.

My mother hears or overhears somewhere that the heiress of Mr.Allegre is contemplating a secret journey.

All the noble Salons were full of chatter about that secret naturally.

So she sits down and pens an autograph: 'Madame, Informed that you are proceeding to the place on which the hopes of all the right thinking people are fixed, I trust to your womanly sympathy with a mother's anxious feelings, etc., etc.,' and ending with a request to take messages to me and bring news of me.