Nicola Bulley's partner Paul Ansell has been asked whether the missing mum had any "enemies or stalkers", over fears she could have been abducted.
The 45-year-old mum vanished on January 27 during a dog walk along the River Wyre in Lancashire, after dropping off her two children at school.
Her phone was found on a bench overlooking the water along a towpath in the village of St Michaels and springer spaniel Willow was wandering alone nearby.
Since then a major police search has been launched, including divers, drones and helicopters.
It comes as Paul was today pictured at the search scene being briefed by police.
Underwater forensic team Specialist Group International (SGI) was drafted in this week and has spent two days trawling the river with a high-tech sonar.
Firm chief Peter Faulding spoke to Paul after the first day's search on Monday night.
He said the 44-year-old dad was "distraught", but he was keen to keep him up to date with his team's progress.
Speaking yesterday, Mr Faulding said: "I spoke to Paul last night and asked him if she had any enemies, any stalkers, the normal questions you would ask.
"And nothing, he said no. And she was totally normal that day when she left, nothing out the ordinary."
The 60-year-old expert is renowned for solving similar difficult cases quickly, and had predicted that if Nicola fell into the river at the bench, his sonar would pick her up in minutes.
However, with no sign of her, he believes more than ever that a third party could be involved.
Mr Faulding admitted the case baffled him, telling LBC "she's just disappeared like she's been taken by aliens".
He told ITV's Good Morning Britain: "I personally think if I rule this stretch of river out today where we're working I don't think she's here, I think there's probably a third party involved."
However, Lancashire Police has ruled out foul play, with Superintendent Sally Riley yesterday playing down Mr Faulding's theories.
Asked about Mr Faulding's comments at a press briefing, Supt Riley said: "I thank SGI for the help they've given to the team.
"Our search has not found Nicola in the river and any research done in parts by SGI found the same.
"That does not mean that Nicola has not been in the river. And in light of other inquiries being discounted from the investigation so far - although we are keeping an open mind to anything new - then clearly our main belief is that Nicola did fall into the river.
"Clearly Mr Faulding isn't included in all the investigation detail any more than the members of the public are that I'm briefing through these sorts of press conferences.
"We would ask that we be allowed time to continue with those inquiries and release to the public only what is relevant."
