The forensic search expert looking for Nicola Bulley has said the case is one of the most "baffling" and "unusual" investigations he has looked into in 25 years.
Peter Faulding, who was brought in by Nicola's family, has suggested that the phone could have been positioned on the bench by the river as a "decoy", Wales Online reported.
"After 25 years of doing this kind of work, after hundreds of cases, I am well and truly baffled. Normally you would expect the divers to find them easily.
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"The police have nothing to go on. All they have is a mobile phone at the moment and they said it could possibly be a decoy," he said on TV.
The 45-year-old mother of two disappeared while walking her dog Willow along a tow path on the River Wyre in Lancashire.
Specialist Group International (SGI), run by Mr Faulding, came to the scene on February 6. They have put to use advanced sonar equipment as part of the search.
The forensic expert said that "the only thing the police have to go on" is her phone on the bench. He believes it could have been put there as a decoy. She was still logged onto a work call at the time.
There has been talk about Willow the dog and if Nicola fell into the river trying to rescue her.
The dog was found by the bench, bone dry and on its lead.
Mr Faulding told GB News earlier this week: "We dealt with a drowning a couple of years ago where a gentleman went into a river and Ripley, his dog, was screaming by the riverbank when we got there.. When we arrived it was howling, and literally pointing exactly where he was. He stayed with his owner."
Witnesses have been traced, however, no additional information for the investigation was gathered.
Mr Faulding said: "People have been walking past the bench. There's no police tape up. This would normally be sealed off as a crime scene so potentially crime scene investigators can go in and see if there are any microfibres, evidence, slip marks down the bank etc and I don't believe that has actually happened here."
He also stressed that sometimes bodies can get lodged in reeds and months later, the sonar won't go into the reeds.
When asked if Nicola could be in a different part of the river, Mr Faulding, who is a forensic diver said: "Unless someone's put her in a different part of the river somewhere or she's fallen in somewhere.... It is a very short stretch. On a normal river we can scan ten miles a day for a body and locate it very quickly."
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