The man, aged about 70, was seen in the River Wyre area around the time Nicola Bulley disappeared.
Image source, Police handoutFriends and family of a woman who vanished while walking her dog say they still have hope she will be found alive as the search for her continues.
Nicola Bulley, 45, was last seen walking next to the River Wyre off Garstang Road, in St Michael’s on Wyre, at about 09:15 GMT on Friday.
Her phone was found on a bench near the riverbank, still connected to a work call, Lancashire Police said.
Ms Bulley’s friend, Emma White, said the situation was “a nightmare”.
A major search is under way involving police, the fire service and mountain rescue teams, after Ms Bulley’s dog was found close to where she disappeared.
‘Overwhelming support’
“Our ultimate priority is to find Nikki,” said Ms White. “We still have hope.
“We don’t know what’s happened, it was just a normal day in a normal life.”
On Monday Ms Bulley’s partner, Paul Ansell, said it was “perpetual hell” for her family.
Image source, PA Media
Speaking from their Inskip home, he said: “We are living through this but it doesn’t feel real.
“All we can say is we need to find her. She’s got two little girls that need their mummy home.
“We have got to get some good news now.”
Members of the community have joined the search for Ms Bulley, also known as Nikki, with friends and family setting up a base at the village tennis club to co-ordinate volunteers.
Ms White said: “The community, friends, people from all walks of life have just pulled together and have done a fantastic job in offering support, which the family need right now.
“It’s overwhelming. I must have got 100 messages a day from people I don’t even know just offering us support.”
‘Open mind’
In a message to her missing friend, Ms White told BBC Radio Lancashire: “We’re missing you immensely and we’ve got two little girls who want to see their mummy. If you are out there Nik come on, come back, we need you, we love you lots.”
Ms Bulley, who works as a mortgage adviser, is described as white, 5ft 3in (1.6m) tall, with light brown shoulder-length hair.
She speaks with an Essex accent and was last seen wearing a long black gilet jacket with a hood, black jeans and olive green ankle wellies.
As well as Inskip and St Michael’s, Ms Bulley also has links to Thornton Cleveleys, Lancashire Police said.
Supt Sally Riley said the force was keeping “a really open mind about what could have happened but we do believe that the likelihood is that Nicola has gone missing and this is not a crime inquiry”.
She urged “anyone who may have been driving through the village of St Michael’s last Friday morning… or who may have dashcam footage that could be of use to us, or people who may have been dog-walking in the area or on the tow path to come forward”.
Why not follow BBC North West on Facebook, Twitter and Instagram? You can also send story ideas to northwest.newsonline@bbc.co.uk