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If the $17.1 million winner doesn't step forward to collect their mammoth prize in the coming days, the PI will be hired to help hunt them down.
The investigator would have a few tricks up their sleeve.
Specific information about the winning ticket could be uncovered, including when and where it was bought and whether an Eftpos or credit card was used.
If Lotto doesn't hear from the winner in the "next few days" they would make every effort to find them, head of communications Marie Winfield said.
"We have some snippets of information about the winning ticket to pass on to a private investigator to locate the missing millionaire," she said.
"We're assuming they are enjoying an extended summer holiday and what a lovely surprise they have waiting for them."
The winning ticket was sold at The Market Store in Twizel on December 28.
A total of $17,166,667 was won with $17m coming from Powerball First Division and $166,667 from Lotto First Division.
Yesterday, the Herald revealed a potential $21,738 of the massive Powerball First Division jackpot had inadvertently been lost in pre-tax earnings.
If the $17.1m was in the winner's bank account as of January 13, in a 12-month term deposit they could earn an interest rate as high as 2.9 per cent per annum.
The numbers equate to $495,900 in pre-tax in the first year. It also equated to around $1358 being lost in potential pre-tax earnings every day.
But Lotto wasn't too stressed, Winfield said, as it expected the winner to claim their prize soon.
Players often stored-up tickets, checking them all at once - last week a $1m from mid-December was found after a ticket was checked.
And in Lotto's history, a private investigator had only been used in a handful of instances when prizes went unclaimed for some time.
Of those, one of the most notable was in 2013, when a winner of a $22m Big Wednesday draw was tracked down.
The winner thought the gigantic prize had already been claimed and was taken by surprise when Lotto knocked at the door, Winfield said.
"We're able to drill down and find specific information about the winning ticket. We were looking for anything that would help us find the winner," she said.
"In that case, some things didn't go our way – the customer paid cash – but we had some good luck while working with the staff at Pak N Save Riccarton, and before long we found some video footage that narrowed our search down to one person."