I'm not quite sure how to answer that question. Should a passport go missing, it's immediately deactivated and that passport can't be used. It is never reactivated. So should it show up again at the mission, it can't be reused by anybody and we've issued a duplicate passport to the bearer.
If the bearer hasn't reported it lost or stolen and it suddenly shows up, generally an investigation is opened. Any number of things can trigger an investigation. You do see patterns. We know parts of the world where there are patterns of passports being declared lost and citizens then coming in to get replacements. We work very closely with our partners in CBSA and the Department of Citizenship and Immigration who are posted abroad to resolve just those situations.