LENOX — It was the end of last Sunday's Boston Symphony Orchestra matinee in the 5,000-seat Koussevitzky Music Shed. Longtime Tanglewood concertgoer Barbara Roney was applauding especially vigorously.

Moments later, she discovered, to her horror, that the diamond stone setting of a birthday gift ring from her husband, John, had disappeared.

"I was clapping uproariously," she remembered. "I think it just flew off."

So, who are you going to call?

The lost-and-found office of Tanglewood's Patron Services department, of course.

That's what Roney did, with faint hope that the microscopic diamond might be recovered.

What she didn't know was that Roger Goldin, a Pittsfield resident since 1978 who retired four years ago after nearly 38 years as director of the psychiatric clinic attached to the Berkshire County court system, would be on the case.

Goldin, a lifelong music lover and devotee of Tanglewood for nearly a half-century, joined Patron Services last month.

"I thought after I retired it would be really nice to work here," Goldin said during a chat on the porch of the Visitors Center at the Tappan House.

Having noticed the opening for a part-time Visitors Center representative posted on the BSO's website, he was interviewed and hired by Amy Aldrich, a Pittsfield native and now a Dalton resident who has worked for the orchestra for 23 years, starting in the box office while in high school. She's now associate director of Patron Services for the BSO, Boston Pops and Tanglewood, working remotely from the Berkshires between summer seasons.

Her many tasks include overseeing the lost-and-found room, a mini-warehouse bursting at the seams with prescription eyeglasses, phones, jewelry, cameras, car keys, driver's licenses and other personal IDs, an envelope full of cash, credit cards, wallets, purses, tennis rackets, scarves, sweaters, jackets, coats and other clothing stored at the new Welcome Center near the Main Gate.

It's all sorted out, organized, scrupulously tracked and logged in on spreadsheets maintained by Aldrich, and, much to her amazement, the items often are never claimed. After keeping them for one year, they are donated.

"It's interesting how much we get in here and to see what might be a valuable item that no one ever calls looking for," she said.

Perhaps not too surprisingly for a forensic psychologist, Goldin quickly developed a detective's knack for finding missing items on the Tanglewood grounds.

"If people knew or had a good sense of where they might have lost something, I would just go there and see if I could find it, the most direct route," he said. He already had recovered items lost at Ozawa Hall — personal reading glasses, a $300 car fob (keyless entry device) and a Tanglewood Music Center student ID badge.

On Tuesday morning, Roney showed Goldin her forlorn-looking ring, minus its setting, and told him her exact seat location.

And then, on bended knee and armed with his iPhone flashlight, Goldin took to the clay floor and inevitable muck in a front section of the Shed.

"My co-workers are kind of skeptical about finding anything in the Shed, especially a diamond," he acknowledged. "But, who doesn't like a good challenge?"

On his first try Tuesday afternoon, just after Roney reported the loss after her own search had turned up empty, Goldin discovered that "it's not just dirt but also metal posts under the seats and all sorts of crevices and things in the metal. It's not easy down there, so I looked and looked and looked. I could not find it. I went back to work, but it was bothering me. Something kept saying to me, `Go back, go back.' "

During his second attempt, "I started rooting around with my finger in the dirt. I kept looking, and all of a sudden my light caught a sparkle, like a glint. Digging some more, I picked this thing up and I couldn't believe it. It was an incredible feeling to find this yellow diamond, I was so happy that I was going to be able to tell her it was found."

Understandably, returning to the lost-and-found treasure-trove, "my only worry was, don't drop it on the way back, you'll never find it again."

Back at the lost-and-found, Goldin left a voicemail message for Roney with the good news.

Two days later, though Goldin was off duty and out of town, Roney returned from her Providence, R.I., home near Narragansett Bay, walking into the Welcome Center while wearing a big smile.

"It's the most fabulous story. I couldn't believe it when I got his message!" she exclaimed, beaming. "It seemed like a needle in a haystack. My husband gave me the ring seven years ago, an unexpected birthday present, and told me to wear it all the time, don't save it for special occasions. So, I thought it was beautiful while I had it. It's a valuable stone. I don't know how much it was worth; it was a gift."

For Roney, the most significant aspect of the experience "was just the kindness of one person listening to another person; something about it made Roger go and look, for which I'm very grateful. Tell Roger I'm madly in love with him."

Later, asked if anything ever went missing for him, Goldin paused, then mentioned "real loss" — the death of his wife two-and-a-half years ago.

Not surprising for a psychologist, he offered some deeper thoughts about "not just finding a person's diamond, it's dealing with loss. This resonated with me; there was an overtone to this story, just like in music."

In a follow-up email message Saturday, Goldin wrote that "seeing that ring torn apart, having lost its centerpiece, produced in me a strong desire to reunite Barbara with her diamond. I wanted to make this whole. Diamonds usually carry personal stories. So this touches on loss and separation, important themes in all our lives, and the universal longing to be reunited with those we have loved and lost."

And he was very pleased to find a thank-you card from Roney, who happens to be a psychoanalyst still in practice.

"As well as being delighted by the return of the lost diamond, I was and am so moved by your attention and determined hunt to search and recover. I was delighted by your kindness and willingness to go beyond," the card stated in part.

Strolling the grounds back to his post at the Visitors Center, Goldin described the BSO's summer home as "a very healing place, between the nature and the music if you're the kind of person for whom music resonates, whatever kind of music it is. It soothes and consoles you when you need it, it makes you happy, or sad, but it bypasses words and goes directly to your heart and to your soul. And kind acts are more likely, because you're cared for here, and you pass it on."

Clarence Fanto can be reached at cfanto@yahoo.com, on Twitter @BE_cfanto or at 413-637-2551.