Police have searched an area of bushland near where a bicycle that could belong to missing man John Norrish was found at Mathinna.
Mr Norrish was last seen at Quayle Street, St Helens on November 28 last year.
The 52-year-old has an acquired brain injury.
Tasmania Police Inspector Michael Johnston said a roadworker clearing the culvert picked up the bike in his machine's bucket at Mount Albert Road.
The discovery was reported to and taken possession of on October 25, but it had been unearthed several days before police were notified.
"The bike has sustained damage, but as a result of the forensic examination we are confident that has occurred when it has been picked up in the bucket," Inspector Johnston said.
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Mr Norrish's nephew Rodney Williams said it was shocking that they still don't know what happened to his uncle.
"We don't know whether he has been murdered or got lost in the bush," Mr Williams said.
"The main thing is to bring some sort of closure to it. I don't know if they're going to find him, but I hope they do."
Mr Norrish is described as being about 174cm tall, slim build, fair complexion and with a long and pointed brown beard.
He was last seen in the St Helens area wearing cream cargo-style pants, a dark coloured zip-up jacket and black Blundstone boots.
Mr Norrish walks with a pronounced limp and is known to ride a red mountain bike.
Weather permitting, police plan to conduct another search in the area next week.
Anyone with information is asked to call police on 131 444 or Crime Stoppers on 1800 333 000.