For four weeks a large-scale search of the Bo’ness area and beyond took place involving officers, search dogs and the force’s marine unit.
On several occasions members of the community joined in public searches in the hope of finding the 64-year-old alive.
Only last Friday, four weeks after he was reported missing from his home in Panbrae Road, an ‘anniversary appeal’ was issued by police asking for anyone with information or sightings of Mr Mouat to get in touch.
Then shortly before midnight on Saturday it was announced that a body found in the Mouat home that afternoon was believed to be the missing man.
The grim find is understood to have been made by a family member in a stone-built garage at the back of their home – a building already searched by officers.
Police said Mr Mouat’s death was currently being treated as unexplained, however the circumstances are not believed to be suspicious. A report will be sent to the Procurator Fiscal.
In his statement, Superintendent Martin Fotheringham of Forth Valley Division said: “This is a tragic set of circumstances and our thoughts and sympathies are with the Mouat family as they come to terms with their loss.
“Following a review of our response to this incident, Police Scotland has referred this matter to the Police Investigations & Review Commissioner (PIRC).
“We will provide them with all the necessary assistance and support they require during their investigation.”
However, only ten months ago, the same police chief, who is in charge of the division’s operations, made a similar announcement following the death of a 46-year-old man in Dunipace.
In this case David Penman’s body was found on December 15 in a van parked on a rural road near Northfield Quarry.
It is understood that police had received several calls from residents in previous days concerned about the vehicle and the fact it had not moved.
At that time Superintendent Fortheringham said: “Police Scotland has reported the circumstances surrounding the discovery of a 46-year-old man’s body within a van, which was parked in the Dunipace area of Denny on Thursday, December 15, to the Crown Office and Procurator Fiscal Service.
“The matter has now been referred to the PIRC. We will provide any necessary assistance to the PIRC as they conduct their investigation and we await the outcome of their report.”
This week, a spokeswoman for PIRC confirmed that its report into the circumstances surrounding Mr Penman’s death had been sent to the Crown Office and it now awaited a response.
In 2015, a Falkirk couple were found in their crashed car, days after the vehicle was reported to police by a worried member of the public.
Tragically John Yuill was already dead and his girlfriend, mum-of-two Lamara Bell, died from her injuries a few days later.
The pair had been reported missing by concerned family members and police had issued photographs appealing for help to trace them.
Despite a major investigation, there is still no decision whether a fatal accident inquiry will take place or if anyone is to blame.
Police Scotland handle around 20,000 missing person inquiries every year.
Earlier this year the force issued an apology after a PIRC investigation identified failings in the search for an 88-year-old Glasgow woman who was later found dead.
The body of Janet McKay, who suffered from dementia, was discovered in Clydebank in September 2015, eight days after she was seen leaving her home. In its report, PIRC said there were “procedural and investigative failings” in the subsequent inquiry.
A spokesman for the PIRC said: “The Police Investigations & Review Commissioner is conducting an investigation into the response from Police Scotland to the missing person investigation for Arnold Mouat following a referral from Police Scotland. The PIRC investigation will focus on the initial response from Police Scotland including the search of his home address.
“This investigation is in the very early stages and a report will be sent to the chief constable in due course.”
Angus MacDonald, Falkirk East MSP, said: “First and foremost my thoughts and sympathies are with the family and friends of Arnold Mouat at this difficult time.
“I am pleased that Police Scotland have referred themselves to PIRC as there are clearly a number of questions with regard to how this search was handled.
“It is imperative that the PIRC investigation is made public and procedures are improved as a result.
“As a rule, Police Scotland conduct missing persons competently therefore lessons must be learned from the outcome of this inquiry.”
The Mouat family only moved to Bo’ness three years ago, living in an impressive detached property next to Bo’ness Old Kirk, having previously lived in Shetland, Aberdeen and Wales.
Neighbours spoke of a quiet man, who was regularly seen out walking. One said: “The police were in our garden checking and looking everywhere. I can’t understand how they didn’t find him in his own property.”
Mr Mouat’s family paid tribute to him in a statement, saying: “We are devastated by the loss of a loving husband and father and we are now trying to come to terms with what has happened.
“We would like to thank everyone for the support we have received over these last few difficult weeks but would now ask for our privacy to be respected so that we have the time and space to grieve in peace.”