David Whipple of St. George said he bought the hamburger -- topped with a pickle, mustard and ketchup -- July 7, 1999, at a McDonald's in Logan and let it age for a month for a lesson on enzymatic action he gave to a group of weight loss advocates, KSL-TV, Salt Lake City, reported Wednesday.
"At the little meeting, I showed the hamburger and the pickle, which was just starting to disintegrate," Whipple writes. "There was no decomposition to the meat or bun, nor any mold, fungus or smell. It had no bad odor at all."
Whipple said he put the burger in his jacket pocket, where it spent a summer in the trunk of his car before being discovered in a closet a year or two later.
"It was purely a fluke about hanging on to it," Whipple said.
Whipple said the burger has since survived without refrigeration or any other types of preservation and still looks like it did the day he bought it, sans pickle.
He said he does not know how the burger managed to survive for so many years without any signs of mold or decomposition.
"That's the million-dollar question. They dig up things in King Tut's tomb," he said. "It's going to take a smarter person than I am to figure that out."