An Oyster Bay Vietnam War veteran is in search of a priceless memento of his military service.

Walter Benka lost a hat that is rich in sentimental value. It happened June 30 at Theodore Roosevelt Park.

The hat is a symbol of his service aboard the U.S.S. Duluth warship when he was a 17-year-old gunner’s partner.

“It meant a lot to me,” Benka says. “My history on that ship, what that ship meant to me and how it formed me as a person, how to be a man.”

The hat was lost when he got into what he thought was his blue Equinox SUV.

Benka says he usually parks in a certain spot that someone else was parked in, so he jumped into the car, which happened to be the same kind of car he has. He says when he got in the car, he took off his hat and threw it in the back seat before realizing he was in someone else’s car.

Benka got out of the car and apologized to the car’s owner, but he didn’t realize he left his Navy cap in the car until hours later.

“The next day actually, I look in the back seat for my hat in my car,” Benka says. “I said, ‘Oh man, it’s in somebody else’s car. We didn’t exchange names.”

Benka’s daughter launched a search on social media with a plea stating, “We know it is a long shot, but if you found this hat in your backseat, if you could please contact me as it’s important to my dad and can’t be replaced.”

The hat has a Vietnam pin on the front symbolizing Bena’s two tours of duty.

It also has the letters “XO” on the back because it was a gift from the executive officer of the U.S.S. Duluth ship.