We will never know who took the note, if indeed one was ever in the envelope. To ship items of value to many countries is the same as throwing it away, it never gets there. Eastern Europe, and Italy are amongst those countries.
While theft in the mails is small in Canada, it is high in many other countries. It is likely in this case that the item had been removed outside of Canada.
A little tip. Before signing and accepting registered mail from outside of North America, inspect the package. If it appears to be tampered with, refuse it. Once you sign for it and accept it, it is yours.
Rick