Nicola Bulley's partner believes her phone on the bench could be just a 'decoy' as he said he remains '100% sure' she isn't in the river.
The missing mum's mobile was discovered still on a work call when it was found by a dog walker two weeks ago.
The 45-year-old was last seen walking pet Willow after dropping her daughters off at school in the small village of St Michaels on Wyre, Lancashire on January 27. Police believe there is no criminal element.
Paul Ansell has spoken in an interview and talked presenter Dan Walker though 'unprecedented hell' as 'nothing seems real'.
The 75-minute special programme 'Vanished: Where is Nicola Bulley?' hits our screens on Channel 5 tonight.
He said: "We always felt that the mobile phone and the harness could possibly be a decoy. Again, we don't have evidence."
Dan asked him: "But these are things that you naturally would think about because, you know, the team's call was still active at the time, wasn't it? And Willow's harness is on the floor and, you know, I'm sure these are things that constantly you are thinking about."
He replied: "Of course it is. I mean, the only thing we're bothered about is finding her - nothing else matters.
"So you're gonna be thinking this, these, these things."
Distress Mr Ansell says that the family haven’t given up her - as she wouldn't give up on anyone else.
"What we’re going through now is like unprecedented hell," he tells the presenter.
"But that hope and that positivity in me is stronger than ever, and I’m never, ever going to let go. Nicky would never give up on us ever.
"She wouldn’t give up on anybody. And we’re not gonna ever give up on her like, we’re going to find her.”
The search has been underway since Nicola, known as Nikki, to her friends disappeared while walking her dog near the river in St Michael's on Wyre in Lancashire, on Friday, January 27.
“Extensive searching, as you’re probably aware, has gone on in that river," he told Dan.
"The fact that the divers and underwater rescue team and all that were in that river on the day, and thankfully found absolutely nothing, in the part where you would have to presume is her last known location.
"Personally, I am 100 per cent convinced it’s not the river, that’s my opinion.”
"Because people don't just vanish into thin air, it's absolutely impossible. So something has happened.
"Something has happened. Find out what it is. Find out what it is.
"There has to be a way to find out what happened, there has to be. You cannot, you cannot walk your dog down a river and just vanish into thin air. Something happened that day, something.”
Lancashire Police launched a massive search and were seen combing the river bank, utilising diving teams, search dogs, drones and boats to no avail.
He refuses to point fingers at the police, despite no news two weeks on.
The force are this afternoon trawling underneath a bridge more than seven miles from where the mortgage adviser was last seen.
“I have to categorically say I cannot fault the police in any of this, they have been incredible, and the relationship that we have working on this is still very, very strong, it’s very good," he added.
"So this isn’t any criticism of them at all, I just want to make that clear.”
The bridge is about halfway to the estuary from the village.
Images show specialists in a small boat travelling around and under the road crossing.
It comes as the search has already expanded to the Irish Sea.
Police have said their "main working hypothesis" was that she fell in a river but a body has not yet been found. However, they insist they are keeping an open mind.
