Funny you mention this! It WAS there several years ago when I first came to Paris and when I went to the Carnavalet a few days ago I looked for it and it was gone. They've replaced it with that painting of Thermidor. I asked the guard if he knew what had happened to the letter and he said, "They removed it." That's all. I stupidly forgot to ask if it was a permanent switch or what, but seeing as how it's been gone for several years...