Doctors feared father-of-two Paul Baxter had cancer after a dark mass was found on his chest - only to discover on the operating table it was part of a police traffic set he had received as a seventh birthday present.
The postman had initially been referred to his local hospital after months of ill health, complaining about a persistent cough.
Amazingly Paul, who is now 50, cannot remember inhaling the cone.
He said: "Kids eat things and I obviously chewed on my toys. But I can't even remember swallowing it to be honest.
"I have been told that I must have inhaled it for it to go into my windpipe.
"If I had swallowed it, it would have gone into my stomach and out the other end."
Healthy Paul said he initially went to hospital before being referred for a bronchoscopy - where doctors sent a camera into his lungs - to see if they could find what was causing the niggling cough.
Paul, who lives in the village of Croston, Lancs., with his wife Helen, 46, said: "Doctors said they could see something orange down my throat but didn't know what it was."
Dr Mohammed Munavvar, has been a doctor for 30 years, was the man who discovered the tiny toy.
He said: "I have never come across something quite this extraordinary before. There have been one or two other things but nothing quite like this."
At first, Dr Munavvar feared the worst, with Paul being a former smoker and having been coughing up yellow mucus for months.
"There was concern about something more serious underlying the problem Paul was experiencing," Dr Munavvar said.
"It was honestly a full on surprise when I saw what the blockage actually was."
Dr Munavvar, who has spent 20 of his 30 years as a doctor at Royal Preston, said: "Usually the patient remembers they have inhaled something but in Paul's case he just didn't.
"We are really pleased for him. The end result was fantastic. The entire team was lifted as a result - we always feel so much better going home improving a patients condition."
Paul said: "The operation was under local anesthetic and when they removed the cone in the theatre it was hilarious, everyone in the room just laughed.
"It has come out in perfect working order, you can even still see the markings."
There was a chance for the toy to find the light of day when Paul was admitted to hospital with a bout of pneumonia more than 20 years ago, but it was never spotted.
And again in 2004 when Paul had a full body MRI scan when he had a brain abscess.
Paul said: "When I was 18 I had pneumonia and I was in hospital for two weeks and even then doctors never picked it up on the x-rays that were taken."
The doctor presented the cone to Paul and he's now kept it as a souvenir of his ordeal.
He said: "I thought it was just a normal chest infection. I wasn't aware of how serious it could have been."
Experts said it's likely he went symptomless for so long because of how young he was when he ingested the toy, suggesting that as he grew older, his airways adapted around the foreign object.
The case came to light after it was written about in the BMJ Case Reports medical journal.
In the journal, doctors wrote: "He finally found his long lost traffic cone in the very last place he would look.
"To our knowledge this is the first reported case of a tracheobronchial foreign body that was overlooked for 40 years."
Doctors said, his symptoms lessened almost immediately after the operation, which took place in 2015 when Paul was 47.
They said: "Four months after removal of the tiny traffic cone, his productive cough had almost entirely settled and a chest X-ray only showed minor residual consolidation."