The patient, James Wataroh, 29, had been admitted to St Mary's Hospital, Paddington, and was detained on the Valentine Ellis ward on the ninth floor.
Mr Wataroh's family has now demanded an urgent inquiry into the circumstances of his disappearance, and St Mary's Hospital officials are trying to piece together his missing hours.
Mike Blakemore, a spokesman for the hospital, said yesterday that Mr Wataroh had been reported missing from Valentine Ellis ward at 6pm on 3 February and 'a very full search' of the hospital had taken place.
Mr Wataroh was eventually found the following evening at 5.30pm by a lift engineer, Mr Blakemore said.
'Unfortunately, we were not able to find him in the search. There was concern because of his condition. (Hospital) procedures were followed; there was a search and his family and the police were informed that he was missing.
'The patient was not in the lift for the full 24 hours, because the lift was inspected between 12 noon and 1.30pm on 4 February. He must have gone in sometime after that,' Mr Blakemore added.
Where Mr Wataroh was before he was found remains a mystery. 'We are continuing to investigate this unfortunate incident actively,' Mr Blakemore said.
The lift in the 10-storey building was reported out of order at 6.20am on 4 February; the engineers took over at 8.20am and began working on the lift at midday.
Mr Blakemore said they were satisfied that Mr Wataroh had not suffered any ill effects as a result of his ordeal. Mr Wataroh is still being treated at the hospital and his condition is comfortable.
Mr Blakemore said that the lifts at the hospital were heavily used and 'had problems like everyone else's lifts'.
He added: 'We will be writing to his family in the next few days to keep them informed.'
The patient is not the first to be lost after admission to a hospital. In November, Elsie Westron, aged 89, died after she had been 'lost' for four hours by medical staff at Greenwich District Hospital, south-east London.
Mrs Westron had been taken to the hospital by ambulance, but died later on a ward from a heart attack. Two doctors said at her inquest that they had been unable to find her.
Security in hospitals is notoriously difficult to maintain, with unrestricted access for members of the public and patients.
Last year, NHS executives called on hospital managements to tighten up their security to try to reduce the levels of burglary and vandalism inside hospitals.Reuse content