ANXIOUS friends and family pleaded with police to search for Rosemary Snell, 67, and Michael Rolfe after they went missing on July 8, 2012.
Their bodies were found nine days later buried under tons of mud after a landslip at Beaminster Tunnel.
At an inquest into their deaths coroner Sheriff Payne said it was concerning that the couple lay undiscovered for so long – but nothing could have saved them.
He said: “Obviously it is a matter of great concern that they were not discovered until nine days later but discovery even minutes later would not have made a difference to the outcome.
But if the pair had only driven through seconds earlier they would have survived, the inquest heard.
Following a day-long hearing at County Hall in Dorchester on Monday Sheriff Payne ruled that 72-year-old Michael Rolfe and 67-year-old Rosemary Snell died as the result of an accident which 'could not have been foreseen'.
But he said: “If they had been 30 seconds earlier or later, this would not have happened.”
Mr Rolfe’s son Mark said in the days after the tragedy he reported his father missing only to be told he was probably on holiday.
He asked why it had taken the police so long to find his father.
He said: “It took six phone calls and seven hours to interest the police. Not until the following Sunday when I spent the day with a police officer checking ditches between Beaminster and his home was it escalated.”
And Carol Walker, a friend of Mrs Snell’s, who reported her missing on July 11, lodged an official complaint with Avon and Somerset Police about the delay.
The Independent Police Complaints Commission found police actions had been appropriate.
Detective Superintendant Paul Auger, of Dorset Police, said there had been no information immediately after the landslip that a car could have been under the rubble.
He said: “We would not explore something and put officers in danger if there is no suspicion that someone is there.”
Beaminster Fire Station Commander Mark Greenham added that while thermal imaging equipment was used on the night of the landslip, nothing was detected.
The inquest also heard that no criminal charges will be brought against Dorset County Council following a police investigation because 'nobody could have foreseen' what happened.
Inquest witness Patricia Roberts told the enquiry of the shocking moment she saw the couple's car enter the tunnel ahead of her.
She drove some distance behind another vehicle, but stopped when she was confronted with 'a wall of mud and water'.
Mrs Roberts turned the car around and said to her husband: “I hope they got out okay.”
The mud was reported to be up to 12 feet high, and had crushed Mr Rolfe's Skoda Fabia to less than a metre.
The inquest heard that Mr Rolfe, of Fivehead, Somerset and Mrs Snell, of Misterton, Somerset, died instantaneously.
But David Ashcroft, who owns the land at the southern exit of the tunnel, told the hearing that the felling of 42 trees on the slope since 2004 had led to the land becoming 'extremely unstable'.
He said: “It was a landslip waiting to happen”.
Questions were also raised over the length of time which elapsed between the landslip which killed the couple on July 7, 2012 and the discovery of their bodies on July 16.
Head of Dorset Highways Management Mike Winter denied that cutting down the trees could have led to the landslip.
He said: “A number of trees were felled which were on steep banks and posed a significant risk of falling over.”
Mr Winter added that just two trees and a number of brambles had been cut back on slope at the northern exit of the tunnel, where the fatal landslip took place.
David Clinton carried out an expert report on the state of the land as part of Dorset Police's investigations into the tragedy.
He said: “It is possible the removal of trees from the slope may have contributed to the landslip, but it is unlikely to be a significant factor.”
Dr Clinton said the most likely contributory factors was ground saturation following 'exceptional rainfall', but also burrowing animals and the poor state of a drainage ditch.
He said: “In older constructions such as this tunnel, the slopes are steeper than we would nowadays design them.
“We can't prevent them falling unless we go along and strengthen them, which has been done recently.”
Mr Winter said that £2.5million was spent re-structuring the tunnel, which re-opened in July last year.
He admitted that work recommended in 2011 was not carried out, but said it would not have prevented the landslip.
Giving his verdict, Mr Payne said: “Ultimately what happened was an accident.
“If they had been 30 seconds earlier or later, this would not have happened.”