An unidentified substance

AT 5.00 am one Friday morning a 19-year-old woman was brought into the Accident & Emergency (A&E) department following a head on collision with a van. The young woman had sustained severe head injuries, along with a fractured pelvis and a ruptured spleen. Following resuscitative surgery, the patient was taken to the intensive care unit, where she remained unconscious following her head injury. Two patients from the van were admitted to A&E with minor injuries, and were discharged home mid-morning. When staff checked the woman's belongings and listed them in a property book, they discovered white powder in a small twist of white paper, which amounted to about the size of a pea. Staff present listed the substance in the property book and then locked it in the cd cupboard. Six hours later, following discussion with senior staff, two nurses disposed of the substance by flushing it down the toilet and recorded their actions with a witness signature from a senior nurse and pharmacist. Was this the best course of action from the viewpoint of the seriously injured patient and the other two involved in the van? What opinion would a police officer have?