Paul Johnson’s disappearance is being investigated by police who have mounted numerous searches for the keen walker.
He was reported missing from St Andrews on Wednesday, September 15.
He was spotted on a couple of cameras during his evening stroll, and was also seen by a friend at 10.45pm on Hepburn Gardens after leaving an address in Hay Fleming Avenue on foot around 10:00pm.
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The family have released a statement thanking everyone across Fife who has continued to help search for Mr Johnson.
They said: “For us and our mum, the last four weeks have been the hardest weeks of our lives.
"Our dad is also a grandfather to nine (soon to be 10) wonderful grandchildren who are missing him as much as we are.
“Loved ones, friends and complete strangers have gone above and beyond to help with the search.
"It is impossible to put into words the gratitude we feel.
"People across Fife and beyond, as well as Police Scotland and the countless organisations and companies have united to help find add with the shared aim to bring him home.
"The kind words and selfless acts of the community mean so much. Thank you for everything you have done for us.
“Please continue to keep him in your thoughts, and keep searching.”
Mr Johnson is described as being around 5ft 9in tall and of slim build with grey hair. He was last known to be wearing a blue rain jacket and light coloured walking trousers.
Door to door and CCTV enquiries have been conducted in the area he was last seen, and anyone with private or doorbell CCTV systems in the St Andrews area has been asked to check their systems and provide any relevant footage to officers as soon as possible.
Police Scotland said Mr Johnson is known to go for walks in expansive areas such as local golf courses, including the Balgove, Craigtoun Country Park, and the Strathkinness area.
Extensive searches have been undertaken in these areas with assistance from search and rescue partners, police dogs, and the Air Support Unit.
Tentsmuir Forest has also been searched.
A spokesperson for Police Scotland said: “Despite many hours of searching using a number of resources at our disposal, we have been unable to trace Paul.
If anyone has any information, no matter how small or insignificant it may be, please call 101 and speak to an officer.”