Maurice "Mo" Matthews said Horton visited the cafeteria on his last day before leaving to serve as defensive coordinator for the Arizona Cardinals and asked him how much money he had in his pocket, the Pittsburgh Post-Gazette reported Wednesday.
"I got $20," Matthews responded.
He said Horton then announced, "Sold for $20!" and handed him the keys to his red 1999 Mercedes Benz SL500 convertible roadster.
"I'm like, 'Stop playing with me Ray; don't play with me,'" Matthews said. "The other (workers) were looking at me, their jaws dropped.
"Ray said, 'Hey, you always liked the car, you're a good dude, I know you'll take care of it. It's yours,'" he said.
Matthews said Horton handed over the title and other paperwork when he gave him a ride to the airport the next day.
"I'm still in shock," Matthews said. "I don't think it has hit me yet. I still pinch myself. I look out the window when I bring it to work and I just go, 'Man, that's mine.'"