He had been given his discharge notes to take home with him when leaving the hospital, but when he received an elderly man's notes in the post it sparked him to question whether he was due any more personal notes - and if he was, what had happened to them.
"But they can't answer either question," he said. "So I want to know what kind of information was sent to anyone else. If this is through envelope stuffing, you could have a little waterfall going on here."
He said he had not been notified of whether he was to receive further documents or whether the ones he took with him were it.
Mr Lamont said he immediately rang the rightful owner of the sensitive information, who he said was annoyed when he learned what had happened.
"I said to him, he's lucky I'm a very honest person because if I wasn't then I could've delved into identity theft."
Hawke's Bay District Health Board retrieved the papers on Sunday to return them to the owner.
A board spokeswoman said occasionally a patient's discharge summary could be mailed out after they had left the hospital instead of being given to them at their departure.
She said the health board had apologised to Mr Lamont and the patient whose information he received, and had begun looking into how it could have happened.
"We have apologised in person to Mr Lamont and have also spoken to the patient whose information he received.
"We understand how important privacy is to our patients and any breach of privacy we take very seriously."
Ironically, the board advised the newspaper to exercise caution while reporting this matter so as not to breach the privacy of the man whose notes were wrongly addressed.
The district health board began looking into the issue during the weekend immediately after being advised of the incident, "so we can fully understand how it happened and put in place any corrective steps to make sure it doesn't happen again".
The former patient said he was told an investigation would begin immediately, but said he had "heard nothing from them".
