Yasmin Milburn, who took up the post on Colonsay earlier this summer, resigned weeks after she was asked to investigate the first crime on the island since 2006, in which the victim was her boyfriend, Trevor Crowe.
In June, Mr Crowe had all four tyres on his £25,000 Land Rover Defender slashed, causing £500 damage.
The incident occurred after Mr Crowe was involved in a heated exchange with fellow drinkers at the Colonsay Hotel.
That night, Ms Milburn turned up in civilian clothes to take Mr Crowe home. Next morning, she went back in uniform and the attack on the vehile was discovered.
Yesterday, Ms Milburn, who runs the Hebridean Isles Trading Company, selling wool products, confirmed that she had stepped down as special constable, but declined to give a reason. “It’s personal,” she said.
Asked if her resignation was connected to the tyre-slashing incident, she said: “I have no comment to make on any of it. I am just a private person, wanting to get on with her life.”
Mike McNicholl, secretary of Colonsay Community Council, said the council had been informed about Ms Milburn’s decision.
“The community council haven’t been told why. We have simply been told the special constable has resigned. She had been training for about 13 or 14 weeks and only appeared in uniform for about a month,” he said.
Mr McNicholl said the search for a replacement would now get under way.
“There has never been anything like the tyre-slashing before,” he said. “Now the hunt is on to find a replacement special constable to work with the nearest mainland police team in Oban.
“It’s a very law-abiding island, but it’s good in the summer to have a physical police presence, for visitors to see we are not some sort of Wild West town.”
The three people who filled the special constable role before Ms Milburn were each in post for several years. Mr McNicholl, 62, said it was difficult to find someone because of the island’s population, which stands at 130.
“There are only so many people available and most of them have got two or three jobs already,” he said. “We have a big volunteer Coastguard service, a fire service and an airport fire service. This narrows the number of people available to be a special constable.”
The last recorded crime before the tyre-slashing was theft of £60 from the home of an elderly resident in 2006.
Chief Inspector Alistair Davidson, of Oban police, said the investigation into the tyre-slashing was still under way, but no-one had been arrested.
Chief Insp Davidson said he would be happy to hear from anyone who would like to take up the special constable post, adding: “We are always trying to recruit special constables on islands, particularly where there is no police presence.
“We are looking for working-age individuals who are prepared to give up their time to help the community.”