Poor communication between West Yorkshire officers meant there was a “lack of activity for several hours” while Camille Bowers was missing, the police watchdog found.
Ms Bowers, 72, a vulnerable patient suffering from a psychotic disorder, was reported missing from Fieldhead Hospital in Wakefield at about 9.15pm on May 13 last year.
She was found at her Wakefield home at 11am the following morning, having taken an overdose, and died in hospital three days later.
Details of the case are revealed in the findings of an investigation by the Independent Police Complaints Commission (IPCC), which found that West Yorkshire Police had “clear performance issues to resolve”.
Last night the force admitted it “could have done better” in the case and vowed to learn lessons from the IPCC inquiry.
IPCC investigators found police treated Ms Bowers’s case as “medium risk” when her disappearance was first reported by the hospital.
Officers arrived at the hospital at about 10pm and searched Ms Bowers’s room but not the rest of the building or the grounds. They then visited Ms Bowers’s daughter to collect a photograph of her.
At 10.55pm the officers went to Ms Bowers’s home, which they reported was secure. They claimed to have checked the back garden and said no-one appeared to be home.
The officers then returned to their station to complete a missing person report, which they left with a sergeant as they went out on an operation to prevent burglaries.
A police helicopter flew over the hospital grounds at 1.40am, but nothing more was done to find Ms Bowers until West Yorkshire’s missing persons co-ordinator reviewed the case at 8am.
The officers who attended the hospital had noted on the report that Ms Bowers had never tried to harm herself before but the co-ordinator realised this was wrong as they had misunderstood information given to them.
He upgraded the case to “high risk” and Ms Bowers’s house was searched again, but it was too late. She had broken a rear window to get into her house and taken the overdose.
An inquest into her death concluded with a narrative verdict.
IPCC Commissioner Nicholas Long said: “My sympathies go out to Ms Bowers’ family.
“It is evident from our investigation that the response by West Yorkshire Police to the report she was missing was not as good as it could have been.”
Mr Long added that, while the actions of the officers did not amount to misconduct, the incident was “something West Yorkshire Police must learn from”.
“We will never be able to say whether a more timely police response could have made a difference,” he said, “but it is clear there were missed opportunities and had the risk to Ms Bowers been noted earlier her house would have been searched.
“Instead there was little or no police activity for several hours in response to Ms Bowers’s disappearance.”
A West Yorkshire Police spokesman said the force accepted the IPCC report. “We successfully deal with huge numbers of missing and vulnerable people every year with the overwhelming majority returned to their homes safely as a consequence of thorough and timely enquiries.
“It is very distressing when a relative goes missing and people need to know that when it happens, we will do a professional job.
“We recognise that we could have done better on this occasion and hope the circumstances of this case have not added to Ms Bowers’s family’s distress.