A woman raised the alarm over Nicola Bulley's disappearance after finding her "worried" dog alone next to a deep river.
The business owner, who did not want be named, spotted Nicola's brown springer spaniel Willow running free on the river bank on Friday morning.
She also found Nicola's mobile phone on a bench by the side of the river, under a tree which has a sign warning of deep water nailed to it.
Bizarrely, Willow was running free and the woman found the dog's harness on the floor next to the river.
She called her daughter-in-law who called Nicola's long-term partner Paul, who dialled 999.
The woman, who runs a business in picturesque St Michaels on Wyre, Lancs., said she knew of Nicola and hoped nothing 'bad' had happened to her.
Speaking today, she said: "I saw the dog and I recognised it, but I suddenly couldn't think whose dog it was.
"There was a mobile phone on the bench and there was also something between the bench and the river so I went and looked, and it was a dog harness.
"The dog looked worried so I tied her up and rushed home as I had to go to an appointment.
"I then went and spoke to my daughter-in-law and she immediately knew who the dog was, alerted the woman's partner and that was it - the police were on it."
Mystery surrounds Nicola's disappearance last Friday and a major police search entered its sixth day today.
She vanished while walking Willow on her usual route after dropping her two young daughters off at school.
Her mobile phone was still connected to a work call when it was found, police said.
The business owner added: "I know of her and her partner because I walk around the river a lot to pass the time.
"I always say morning to them or comment on how it's a lovely day but that's all.
"It's just awful, I hope to God that it's not a bad outcome."
Nicola's friend Emma White, one of many locals helping rescue teams in their search efforts, described her as 'the most beautiful person' who is a 'great friend'.
She said: "She's a great friend but she's also a daughter, a sister, a mummy and a partner to Paul.
"She's the most beautiful person the outside but even more so, on the inside.
"She is the most perfect human being as she's kind, caring, loyal and just the greatest friend."
Nicola is 5ft 3ins, with light brown shoulder-length hair and speaks with an Essex accent.
She was last seen wearing a long black gilet jacket with a hood, black jeans and olive-green ankle wellies. Her hair was in a ponytail.
Anybody who has seen Nicola, or has information about where she might be, is asked to call 101.
