The ecstasy of a million-dollar Lotto win quickly turned to frenzied panic for an Auckland man who managed to lose his ticket after leaving it on top of his car and driving off.

The central Auckland man, who wishes to remain anonymous, had an inkling he had the winning ticket when his flatmate told him his local supermarket, New World Victoria Park, had sold the big one on June 29.

"I consider myself quite a lucky person, so when my flatmate told me of the local win, I just a had a feeling it was me," he told the Herald on Sunday.

But the man, in his 30s, decided not to check his ticket for 10 days to extend the dream of what it would feel like to be an instant millionaire.

The dream became a reality when he returned to the supermarket on July 9. "I checked the ticket under the self-checker and came up with 'major prize winner', and I knew it was me," he said.

Any Lotto win over $1000 is classed as a major prize and winners can either fill in a form at a Lotto outlet to have their winnings deposited into their bank account, or claim the winnings at Lotto New Zealand's Newmarket HQ.

The instant millionaire opted to claim his prize in person and have a celebratory drink with Lotto staff.

So he grabbed an envelope to keep his ticket safe and continued on with his shopping.

"I thought I might as well grab a box of beers to take home to celebrate with my mates.

"I got back to my car and as I opened the door, I put the box of beers in the back seat and, for some reason, put the Lotto ticket on the roof of my car."

It wasn't until the winner got home that he realised what he had done.

"I just stood by the car, absolutely stunned at what I'd done - I'd basically just let $1 million fly off."

He grabbed his flatmate and raced back to the store to search for the missing envelope. The pair scoured the carpark with no luck.

They then decided to follow the car's route home and found the envelope sitting in the middle of the road - one of the busiest in central Auckland - just outside the supermarket.

"I couldn't believe it was just sitting there," the winner said. "Now I can say I am truly a lucky person."

A Lotto spokeswoman said systems were in place for winners to try to claim prizes if they lost their tickets, but it wasn't "quick and easy".