ABC News' Alexis Shaw:
Michelle La Plante could not have imagined that a trip to the playground with her daughter over Memorial Day weekend would have her on a mission to track down a stranger who left something very precious behind.
La Plante was at Camel Playground on New York City's Upper West Side on May 27, when she found an engagement ring on the ground near the swings where her daughter was playing.
Thinking the ring's owner would soon return after realizing what she had left behind, La Plante put it in her pocket.
"I picked it up because I didn't trust someone else to do the same. I would hope someone else would do that for me," said La Plante. "I thought someone would come imminently, frantically looking for the ring."
But when no one returned, La Plante did what she would have wanted someone to do for her. She posted signs for the owner, both online and off.
In addition to plastering the park and the surrounding area with "found ring" signs, La Plante posted an ad on Craigslist, as well as a blog post on MyUpperWest.com, a website dedicated to the goings-on in the neighborhood, to help track down the owner.
The owner, Jill Fink, said she "cannot believe that such a good person found [the ring]."
Fink had taken her 2 1/2-year-old twins to the playground with her husband the same day, and took off her ring to apply sunscreen on her daughter. She then rested it on the seat of her stroller and forgot to put it back on.
Fink didn't notice until two days later that her engagement ring had gone missing.
"I looked at my hand on Tuesday morning on the way to work and realized I wasn't wearing it," said Fink. "So I ran back upstairs but it wasn't in my room. Then, I had a flash of putting sunscreen on my daughter and realized it was two days ago."
Already late for work, Fink quickly hailed a cab and called her husband, crying, telling him what had happened.
When she got to work, she thought she would never see the ring again.
But a quick search on Craigslist from a helpful co-worker quickly put Fink in touch with La Plante, who she emailed with details of the ring in hopes that the posting would be a match.
"My ring has an adjuster on it, so it opens up and closes, which is not a common thing," said Fink.
When La Plante received the email from Fink detailing the lost ring, she knew she had a match, and called her to give her the good news.
"She picked up [the phone] and started sobbing and so did I. It was this amazing, happy ending," said La Plante.
The two met on a city street corner that Tuesday morning so that La Plante could finally reunite the ring with its owner.
La Plante said she's gotten positive feedback from strangers since performing her good deed.
"The signs I put up - I got calls from people who left messages that said, 'Hi, this is not my ring and I didn't lose my ring, but I think it's amazing what you're doing and I hope that there's good karma coming your way.'"
La Plante and Fink, despite never having met each other before, found out they had a lot in common. They both live within two blocks of each other and have children around the same age.
Fink said an outing with the two families is in the works.
She had this to say about the fortuitous act of kindness on her Facebook page: "There are really stupid people out there who take their engagement rings off to avoid getting sunscreen on them but thankfully there are also really wonderful people out there who go out of their way to do incredibly nice things for strangers. I am so grateful and inspired."