A private investigator has lifted the lid about how Lotto might be able to track down its missing millionaire.
Since the massive Powerball First Division $17.1 million was struck on December 28, the winner has remained anonymous.
The only thing known about the winner was where they bought the ticket, at The Market Store in Twizel.
However, if they didn't step forward soon Lotto was prepared to roll up the sleeves and hire a private investigator to track them down.
"All you need is a name," Auckland-based private investigator Julia Hartley Moore told the Herald.
But how Lotto might be able to find out the name of the winner was up in the air, she said.
However, Lotto has confirmed specific information could be uncovered, including what day the ticket was bought, the exact time and whether a credit card or Eftpos was used.
Hartley Moore hypothesised Lotto would then be able to uncover the winner's bank account to then get a name, something private investigators couldn't do.
"Your bank account details are private, like your phone records. A private investigator doesn't have any authority to look into those - only the police," she said.
"That's breaching all of the privacy laws but maybe Lotto has other avenues that we don't know about, I don't know."
The only way around being tracked by your bank account was by using cash.
In 2013, video footage from Pak'nSave Riccarton in Christchurch was used to track down a man who was unaware he had won $22 million.
And because Lotto could pinpoint when the winning ticket was bought, identifying the buyer would be a lot easier, Hartley Moore said.
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."
Winners also had 12 months from the draw to claim their earnings, so there was no great rush for the buyer to step forward if they didn't want to.
A total of $17,166,667 was won with $17m coming from Powerball First Division and $166,667 from Lotto First Division.