It is 19:45 hrs in your Emergency Department.

 A 36-year-old man with recurrent depression, alcohol misuse, and a recent suicide attempt is brought in by ambulance after being found sitting on a bridge by bystanders.

 He tells staff, “I don’t deserve to be here,” but initially agrees to stay for assessment.

 While the department is crowded, he is later discovered missing from his cubicle.

He is known to be high-risk for self-harm, and his capacity to decide about treatment was not assessed.

 You are the ED Consultant on duty.

According to the RCEM Best Practice Guideline (2024), what is the most appropriate immediate action after recognising that this patient has absconded from the Emergency Department?