Murdoch (65) was sent home from the All Blacks European tour in 1972-73 and has lived since in outback Australia, but has visited Dunedin occasionally.
The New Zealand Rugby Union is handing out caps to All Blacks from the end of World War 2 to 1997. Capping ceremonies started this month. Murdoch's name was missing from the list for the Dunedin ceremony.
His brother, Bruce Murdoch, of Mosgiel, said he had not heard from the NZRU about a cap for his brother, though he doubted his brother would be interested.
"I do not think he will come back to get it."
Mr Murdoch said he would love to have the cap and would consider giving it to the Zingari-Richmond club, which both brothers played for in Dunedin.
Zingari-Richmond president and club captain Kenny Ball said there had been talk around the club about whether Murdoch would get a cap.
"We'd be proud to have it here. He definitely deserves it. It would be great to have that in the trophy cabinet."
New Zealand Rugby Union chief executive Steve Tew said Murdoch was one of a few All Blacks the union could not locate.
"We have been asking their team-mates and other contacts to try and locate these people and include them in the capping activity. If others know the whereabouts of some of the people we are looking for, including Keith Murdoch, the NZRU would be more than happy to have that information so we can offer them the opportunity to receive their All Black cap."
The union did not have details of more than 40 All Blacks, although most of them had died.
The union would be happy to talk to Bruce Murdoch about awarding the cap.
