(CNN) -- A year ago Thursday, someone walked into a QuikTrip in Des Moines, Iowa, picked up a lottery ticket and hit the jackpot: $16.5 million. For the next year, officials with the Iowa Lottery waited for the person or persons to come forward, but that wait ends at 4 p.m Thursday.
If the ticket goes unclaimed, it will be the second time this week that someone has forfeited a mega payday. On Monday, a $77 million lottery ticket went unclaimed in Georgia.
"Someone legitimately won this money and we want them to take it home," Iowa Lottery CEO Terry Rich said in a news release. "But you must present the winning ticket to the lottery in order to claim the prize."
Few financial advisers would consider the $1 spent on the ticket to have been a wise investment. The buyer overcame 1 in 10.9 million odds to win, said Mary Neubauer, a spokeswoman for the state lottery. If the ticket is redeemed, the winner would owe 25% in federal taxes and 5% in state taxes, she said.
But the possibility of taxes and the absence of a ticket haven't deterred the hopeful from lining up -- just in case. "We've been getting calls from the public all day long today," Neubauer said Wednesday night. "The closer that the deadline gets, the more people seem to be calling."
Some of the calls are from people who say they may have lost the ticket, or put it through a washing machine, she said. They are walked through a series of questions to determine whether they may indeed be the winner. So far, no luck.
Other calls, she said, are from people who believe in the power of their own creativity. Once told they could not have been the winner, they call back again -- and again, each time with a different story, she said.
"That's why we keep emphasizing that it comes down to -- you have to have the winning ticket," she said.
If the prize goes unclaimed, the money would return to the 15 lotteries that offer the game -- in proportion to the percentage of sales that came from each state. "Iowa would get back about $1.3 million if this prize were to go unclaimed," Rich said.
States differ on how they would use the money. In Iowa, the money would go into the prize pools for future games.