"Lost Property: how do I progress this complaint?"

My 90 year old mother was admitted one a week before Christmas , brought in by ambulance. After a short stay on Surgical Assessment she was transferred to Brook Ward where she stayed until 24th December. Shortly after she arrived my sister and I brought her clothes in, expecting her to be released same day. An Emergency Receptionist took these clothes to Surgical Assessment for her as we were not allowed in due to norovirus. Despite 4 phone calls a blue fleece coat and brand new glasses cannot be found. I have also left a message for the Bereavement Officer, who I now understand is responsible for lost property, but have received no response. Please advise how I can progress this complaint.