If you're really curious, check the OLG and OPP websites, they may have posted the means in which the winner was found.
The only reference was the Ombudsman report which identified at least 5 probably large prize fraud cases. The only item I could find is OLG press explanation highlighted below:
The authorities only shared a glimpse of that profile with the public back then.
They revealed the fact the ticket was purchased at That’s Entertainment in St. Catharines and validated at a Variety Plus in Burlington. They said the person who turned in the ticket won a free ticket they never received. That free ticket won the jackpot.
Bill Price, director of the OPP’s Inspection and Investigation Branch, Alcohol & Gaming Commission of Ontario, said that because of the database, they already knew the rightful winner — or winners — lived and worked in the St. Catharines area.
“The ticket profile that we had was very unique and very specific in terms of how the person who was purchasing and validating tickets played the Super 7, in terms of the amount of money spent, the amount of tickets purchased, where they were purchased, the favourite location and also visiting other stores,” he said.
Some of the details of the group’s habits are being kept quiet; a criminal case is now before the courts.
But regular lottery players develop a pattern, Price explained. A person might buy a ticket, win $5 or $10 dollars, and use that money to by another ticket, creating a chain that can be followed.
These winners established such a chain, and a strong one. It went back months before the win and continued afterwards.
....... “It’s like finding a needle in a haystack,” said OLG Chair Paul Godfrey. “We found the haystack and we also found the needle.”
To begin - where the ticket was validated is irrelevant since it was palmed at the store that was first issued and was in the hands of the thieves from that point on.
The only way to absolutely link the the winning ticket to the any specific individual is to identify the ticket and the numbers on it that produced that winning ticket. In New York, a winner was able to recover a stolen ticket from her uncle because she always played the same number, had previous ticket stubs with the same numbers and explained why the numbers were lucky for her. Even though it was stated /rumored that these St Catherine guys played the same numbers - it was a free ticket that won - the numbers were random.
If there was a direct link - they knew the numbers of the ticket that produced the win - it is cut and dry - there is no pattern to follow and the explanation did not have to be cloaked in mystery. Without a link, the number of tickets, spending habits all become probability issues - not 100% proof. I don't think they found a needle in a haystack - I think they drew straws and these guys won. Of course time will tell.