A Powerball ticket worth $16 million became worthless on Friday after a six-month deadline for the winner to claim the prize money expired, Florida lottery authorities said.
"It's only happened a few other times, so this is really, really unusual," said Florida Lottery spokeswoman Amy Bisceglia.
"It could have been anything, from somebody forgetting about it in the laundry, or just throwing it away. We have no idea what happened," Bisceglia said, when asked how the ticket holder could not have claimed the fortune.
The ticket became worthless when a 180-day deadline to claim the jackpot expired at 11:59 p.m. EST on Thursday (0459 GMT Friday), Bisceglia said.
It was the largest unclaimed jackpot in Florida since 2003, when a $53.7 million jackpot expired.
The winning numbers were 2, 6, 19, 21, 27 and a Powerball number of 25.
The winning ticket was purchased in May at the Carollwood Market, a convenience store in Tampa.