Is it necessary to alert an unaware person that a portion of a trust has not been returned to its owners due to his lack of knowledge thereof?

One must alert the person who still has a part of a trust (amanah) for which he is unaware, as a form of sincere advice (naseehah) to a Muslim, and to prevent the loss of another's right. This is in accordance with the saying of Sahib al-Kafaf: "Alerting the heedless to what, if he were to become aware, would necessitate for him some obligatory matters."