Apparently this was an exercise book he made for a parisian tutee, who later fled the french revolution, leading to the confiscation of the notebook by the revolutionaries.
Any time something of popular historical interest like this pops up I think about that.
If you've not read it then Robert Harris's (factual) book about the affair is entertaining, not least because such a broad sweep of dislikeable characters were undone by greed and folly!