Montgomery dedicated himself to returning it, with the only clue to its owner being the inscription "Ruth-Larry 10-21-39."
Two years later, in 1995, he found the widow living in Kentucky and returned the ring.
An Associated Press story that ran in The Herald-Mail caught the eye of the aspiring screenwriter.
At the time, Gabriel, 36, of Halfway, had writer's block. The story provided just the motivation she needed.
After five months of research, using old Life magazines at the Washington County Free Library and writing to Montgomery in Belfast, Gabriel had written her screenplay.
Her story has a Hollywood twist, though.
When Montgomery's character returns the ring, he meets and falls in love with an American woman. But the two must overcome many obstacles to be together, with their 4,000-mile separation being the least of them, she says.
"A lot of people have asked me if I am the girl he fell in love with. I'll just say that I'll leave that to the audience to decide," she said.
She has sent the play to two producers and has been written about in the Irish newspaper Belfast News Letter.
Gabriel is a single mother who works full time as a restaurant manager. She writes in her spare time.
"It's a driving force. Some people write because they have to. I write because I cannot keep from writing," she said.
Gabriel's first screenplay was about the 1994 murder of an acquaintance, Gina Kriner of Hagerstown. She felt it was too personal to sell.
She started writing as a child. At age 4, her father died and she went to live with her grandparents.
Because the family was poor, her grandfather had to come out of retirement and work as a posthole digger to support her, she said.
Her obsession with Ireland began with her grandmother, Anna Elizabeth MaHoney, who was born in Munster County, Ireland.
Gabriel even speaks with a slight Irish accent, no doubt her grandmother's early influence.
"The Irish people are so warm and lovely. There's a lot of great storytellers," she said.
"There's something magical and mystical about Ireland."