Bob Sauer went into his backyard in suburban Portland, Ore., on Sunday night, flashlight in hand, to check if any pieces of the Alaska Airlines plane that had lost a part of its fuselage in midair had landed nearby.
A neighbor had urged Mr. Sauer to check his property in Cedar Hills, Ore., saying she had heard that a cellphone that had fallen from the plane had been found in the neighborhood.
Mr. Sauer quickly caught sight of a white metal object leaning against the branch of a cedar tree. “My heart started beating a little faster,” he said in an interview on Monday, “and I thought there’s no way.”
But it was true: Mr. Sauer, a physics teacher at the Catlin Gabel School, a nearby private school, had found the mid-cabin door plug, which had been torn from the plane mid-flight on Friday, in his yard.
He called the National Transportation Safety Board, which arrived at his house on Monday morning, interviewed him for about 30 minutes and then hauled away the critical piece of evidence from his yard, he said. The board, he said, gave him a medallion emblazoned with an eagle to thank him for his efforts.
Door plugs are used to fill emergency exits that are not needed on planes that are configured with fewer than the maximum possible number of seats. The board said in a statement on Monday that investigators were “currently examining the door plug” and planned to send it to an agency laboratory in Washington, D.C., for further examination.