A Queens woman thought all hope was lost when her 1.3-carat engagement ring worth $13,600 went missing in the sands of Robert Moses State Park — and joked on Facebook that “some broke metal-detector dude” might pocket it.

She was half-right.

There was a guy with a metal detector, but it was a retired city firefighter who did the right thing.

Erin Carrozzo, of Flushing, told The Post she was devastated when her "pride and joy" went missing along with her diamond-encrusted wedding band on Aug. 4, shortly after removing them to apply sunscreen at the beach.

"I never took those rings off except to take a shower on vacation or at the beach," the 41-year-old mom said. "The funny thing is, I wondered if I should leave them at home that morning."

Carrozzo frantically searched the sand, but her bling was nowhere to be found. Heartbroken, she reported the rings missing and left the beach empty-handed.

"I waited until I was in the car to break down," she said. "I kept saying to my husband [Peter], I felt bereft."

But retired FDNY firefighter Mike Cogan, 66, detected the ring two days after it was lost.

"It was absolutely spectacular," he said. "Happy as I was, I realized the poor woman who lost this had to be devastated."

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