The 42-year-old was spotted in Galamuir Drive at around 4pm that day, and since then has not returned home or been in contact with family or friends.
Now police have produced CCTV pictures of a man and woman who were walking dogs on Plean Main Street at around 11pm on that night.
The man is seen wearing a dark coat and is walking a small cream-coloured dog, while the woman has dark hair and is wearing a dark coloured jacket with a fleeced hood and Ugg-style boots.
She was walking a small black dog.
Another man was also pictured outside the Clansman Pub on Main Street around the same time.
He is seen wearing a grey jumper, black jogging bottoms with a white stripe down the leg and white trainers.
All of these individuals may have seen or spoken to Brian before he was reported as missing, and they are asked to come forward and assist police with their inquiries.
Inspector Donna Bryans from Stirling Police Station; “Given the length of time since Brian’s last sighting we are growing ever more concerned for his wellbeing and are eager to hear from anyone who believes they know where he is.
“The people on these CCTV images might have seen or heard something that is of use to our investigation and we would urge them to contact us immediately.
“Anyone with any further information relevant to Brian’s disappearance is also asked to get in touch.”
Anyone with information should contact Stirling Police Station on 101 and quote incident number 2186 of the September 22.