Not if he was in there because of suicidal thoughts—that's what they were supposed to treat!
I had a college mate who lost it and was sent to a psych ward, where they took away all potential items of self-harm. The nurse found her dead in the morning, age 40. She had taken the plastic bag liner from the wastebasket, tied it over her head and suffocated to death.
Psych hospitals are supposed to know how desperate these patients feel.
You are totally correct.
Nursing walks through at least twice a shift to correct deficiencies.