The Council of Community Services in Gillette blamed "human error," The Gillette News-Record reported.
"It was poorly done on our part," CCS Executive Director Carma Harston said.
She plans to write the 340 people who bought $100 raffle tickets to explain what happened.
Harston told the newspaper that the person doing the drawing Friday night picked a ticket bearing the name of Linda Caylor of Moorcroft. But someone in the crowd yelled for a do-over, saying that the tickets should be shaken up more. The drawer followed those directions, put Caylor's ticket back with the others and selected one bearing the name of Jerry Tystad of Gillette.
The organization has been in touch with Tystad, who agrees that Caylor is the winner, Harston said.
Caylor was philosophical about the mix-up.
"I don't win anything," she said. "I usually just donate to things like that."