A terminally ill mother has issued a plea to find out where her missing son’s body is before she dies.

Mystery surrounds the whereabouts of 24-year-old Kyle Vaughan, whose crashed car was found abandoned on a country road in south Wales in 2012 and prompted detectives to launch a murder investigation.

Today, on the third anniversary of his disappearance, his mother Mary has launched an appeal for people to come forward with information. The 53-year-old, who has advanced liver cancer, has been told by doctors she may have just weeks to live. She has said she cannot bear the thought of dying without knowing what happened to her only child.

Mrs Vaughan said: “The doctors have said they don’t know how long I have left. It could be just weeks. If I’m lucky it might be months. I should be able to properly say goodbye to him, to give him a funeral. The thought of not ever finding out is too cruel to contemplate. I just want to know where my Kyle is. Someone out there must know something. I want to say to them: ‘Put yourself in my shoes.’”

Mary Vaughan Photograph: Gwent Police/PA

Vaughan, known to his friends as Jabbers, was last seen at his home in Newbridge, Caerphilly, on 30 December 2012. Later that same night, his damaged silver Peugeot 306 was found on the A467 between Risca and Crosskeys. It was not clear whether Vaughan had been driving the vehicle, but police said they were confident he would have been able to walk away from the collision.

“I knew straight away something was wrong,” said Mrs Vaughan. “Kyle would always answer his phone no matter what – and even when he went away on holiday with his friends he would still always call me up every morning to let me know he was safe.”

Extensive searches by a team of up to 40 officers followed, as well as numerous public appeals for information.

The major investigation has seen detectives sift through a mountain of evidence – including more than 10,000 lines of telecommunications data, 200-plus hours of CCTV footage and about 2,000 separate pieces of property.

“Christmas and New Year should be a happy time, but for us it brings back the bad memories of when Kyle first disappeared,” said Mrs Vaughan. “I can’t celebrate Christmas any more. The only present I ever want is to get my boy back. Being told by police they believe your only child is dead was hard to take, but the uncertainty in not knowing where he is or what has happened has made things worse. It’s like being constantly in limbo. It makes the grief unbearable. I definitely think the stress and the uncertainty has had an effect on my health.

“Someone out there must know what has happened to him or has information which could help the police. Please, come forward. You can give information anonymously if needs be. I don’t have much time left.”

Anyone with information on Vaughan’s disappearance should contact Gwent police on 01633 838111 or 101. Alternatively, contact Crimestoppers anonymously on 0800 555111.