In this case, the trustee was removed as a sanction for failure to comply with discovery. While the trustee was put on notice of a hearing seeking to compel discovery, he was not put on notice that he might be removed as trustee as a possible sanction. As such, the trustee had no reason to be prepared to defend against such a sanction at the hearing.
The trial court order removing the trustee also stated that the sanction of removal was being imposed for failure to comply with previous court orders. As such, removal was analogous to an indirect civil contempt order (i.e., punishment for failure to comply with prior court orders), and civil contempt sanctions require notice and an opportunity to be heard.