"We can't wait to find out who New Zealand's latest multi-millionaire is," she said.
"Very rarely we've had situation where large prize was not claimed - but not of this magnitude."
Lotto advises anyone who bought their Big Wednesday ticket from Countdown Pukekohe South to write their name on the back of the ticket and check it immediately at any Lotto outlet or online at MyLotto.co.nz.
Big Wednesday's wayward winner has 12 months to claim the prize.
Meanwhile, a lucky Aucklander has scooped themselves a $1 million prize with Lotto last night.
The newly made millionaire pocketed the cash after winning Lotto's First Division prize at last night's live draw.
The winning ticket was sold at Pam's Corner Dairy in Glenfield.
Also celebrating last night were 20 lucky dads, who won on the Father's Day promotion, which saw extra prizes up for grabs, including 10 Volkswagen Amaroks and 10 $10,000 cash prizes.