Surgeons left a scalpel blade inside the body of a retired Devon headmaster during a heart bypass operation, it emerged on Thursday.
Victor Hutchison was admitted to Derriford in September 2003.
The blade was not found until three months later when Victor Hutchison was X-rayed at another hospital after being admitted with gall bladder pain.
Mr Hutchison, from Sticklepath, near Okehampton, died from unrelated causes last March aged 76.
Derriford Hospital has apologised to his family for the mistake.
Mr Hutchison was admitted to the Plymouth hospital for heart surgery in September 2003.
Surgical staff realised one of the scalpel blades was missing and spent an hour searching for it following the operation.
Mr Hutchison was given an X-ray but the blade had become lodged in his abdominal cavity, near his spine, not the chest cavity where staff were looking.
It was only when the pensioner was admitted to the Royal Devon and Exeter Hospital in December 2003 and given an X-ray to look at his gall bladder that the blade was discovered.
Derriford consultants decided it would be safer to leave the blade where it was rather than risk another operation to remove it.
Mr Hutchison's widow Joan, 68, said on Thursday it had been an "almost impossible time" for her.
"We just feel that they should have been more thorough at checking."
'Serious clinical incident'
In a statement Derriford Hospital said: "We can only apologise that the surgical blade was left in Mr Hutchison and that the X-rays failed to reveal it at the time.
"It was reported and investigated as a serious clinical incident when it happened, as per our standard procedures.
"We then carried out a further full investigation, which included statements from all staff involved.
"The incident was taken very seriously and we have changed theatre practices to ensure this cannot happen again."
A pathologist found the presence of the scalpel blade did not contribute to Mr Hutchison's death, the hospital added.