The remaining entrance – from Garstang Lane, which leads to the A586 – remains a key target and detectives are keen for anyone with dashcam footage from the area on the day Mrs Bulley disappeared to come forward to help their efforts.
Speaking to reporters after the televised press conference, Supt Riley cast doubt on the idea that an attacker had exploited this small blindspot to successfully target Ms Bulley without leaving a trace of the crime behind.
It was, he said, “so unlikely.”
“When you triangulate all the witnesses, all the CCTV, digital and telepathy, the whole picture creates such a tiny window of criminal involvement that it becomes highly unlikely,” he said.
The location of Ms Bulley’s disappearance makes it more unlikely, police believe.
“This is a low crime area, it’s a really safe, close-knit area where people look out for each other,” Supt Riley said.
“The idea that there is a third party that we haven’t seen yet, haven’t caught on CCTV, dash cam, is not likely.
“But we’re not closing our minds to the fact that there could be new information that we don’t have yet, so we’re continuing at the level of resources that we have.”
This candid stance by a police force in the midst of a missing person investigation is unusual and likely stems from the huge level of public intrigue Ms Bulley’s disappearance has generated.
Supt Riley said rampant speculation on social media about what – or who – had caused the mortgage adviser to disappear was now adding to the dismay of her loved ones.
The officer said: “Our main working assumption is that…there is no third party involvement or criminal activity and that this is not suspicious, but a tragic missing person case.
“This is particularly important because speculation to the contrary could be really painful for Nicola’s family and children.”
Supt Riley, speaking candidly after the press conference, admitted it would be too devastating to think at this stage that there was a chance Ms Bulley would never be found.
“It’s a strange case and it’s strange, but that doesn’t mean that through custody we can’t find answers for the family,” he added.
In the week since Ms Bulley’s disappearance, public interest in the case has escalated both locally and across the country.
Armchair sleuths have, with grim predictability, taken to social media with speculation and accusations about what unfolded by the River Wyre that morning.
Public excitement has reached such a level that the comments under the pictures Ms Bulley posted on her Facebook page have been filled with strangers openly discussing their suspicions that she has been murdered, with baseless claims of guilt.
In one such typical post about the case, posted on Twitter on Thursday night, a social media user claimed to have called the police to report her suspicions about a person she had seen on Facebook.
On Friday, there were signs that public excitement over cracking the case was starting to test the patience of the police force investigating the disappearance.
In a pointed intervention during the press conference, Supt Riley said: “Please the public can only continue to report factual information they have and not speculation about what may have happened to Nicola because this is a distraction from the investigation police and not helpful for the family.”
When The Telegraph later asked the detective for her comments, she revealed that the public’s help to police bordered on the surreal.
“We’ve had a lot of speculative inquiries,” he said.
They included “clairvoyants” who had called the force to offer their help in trying to locate the missing mother.
Supt Riley said other examples included “someone seeing something real and then guessing what that might mean”.
“That’s not helpful,” he said. “If they see something relevant, report that they think it’s relevant – report it and don’t start thinking about what it might mean.
“Anything it takes away from the investigative team’s ability to focus on the facts is a minute or an hour less that we can spend on more credible investigations.”
Earlier on Friday, Mrs Bulley’s partner Paul Ansell, 44, said he would “never give up hope” of finding her.