An Australian man who found a camera washed up on a Queensland beach in October is crediting Facebook and his own dogged sleuthing with helping him track down the Ontario owners six weeks later.

David Castellan said the bright pink camera was covered in barnacles and had been in the ocean for about nine months, judging by the time-stamps on the photos.

"My instant reaction was, 'OK, if I lost my camera, I'd really like it if someone tried to return my photos, because although they meant nothing to me, they probably meant a lot to them,'" Castellan said in an interview Thursday with CBC Radio's As It Happens.

"They looked like they were in love. There was a lot of photos of 'I love you' drawn in the sand, and pictures of them holding hands, shadows on the beach."

Castellan's quest began with a simple analysis of some of the 292 photos in the camera.

"The guy had a pretty distinctive tattoo on his back, a large crucifix and the Italian flag, and I thought they must be from Italy," he said. "And I went down that path for a while, and then the further I looked into the photos, I suddenly realized, 'Hang on, they might be Canadian.'"

Beer gives it away

The brands of alcohol apparent in the photos were a clue, he said.

"Alcohol that people drink is a big giveaway," Castellan said. "And there were a lot of Canadian drinks, a lot of Canadian beer, and yes, the snow was a giveaway."

He also noticed shopping bags with the logo for Montreal-based Le Chateau.

"I thought maybe these people are actually French Canadian and are not Italian after all. The further I looked the more things I found."

The next step was to narrow down where in Canada they might live, which proved just as difficult.

"I didn't realize how big Canada was. And I had a look and I thought they could be anywhere."

His friends recommended trying Facebook, so Castellan started a group on the social networking website, which he called "Do You Know This Couple." The Facebook move brought its own challenges.

"The problem with (Facebook) groups is you have to invite people to join, and unless you know people from Canada it's not going to go anywhere," he said. "So then I just started making random friends with anyone from Canada, especially French Canadians, 'Hey be my friend.'

"And I just started joining groups, any groups that were Canadian-related, like, 'Operation Bring the Spice Girls to Canada,' 'I'm Canadian I can outdrink Americans Anyday,' 'Young drivers against new Ontario law.'"

Photos checked more closely

This effort, too, went nowhere, so Castellan returned to the photos, looking for clues he might have missed.

There was an impressive bridge, and after googling bridges of Canada, then bridges of North America, he learned it was the Mackinac Bridge in Michigan. He guessed the couple were from Ontario and focused his searches there.

Another productive clue was a Christmas photo of a gift book, Karaoke World Domination, on which someone had written an inscription and the name Katey on it.

On Dec. 1, someone on Facebook saw the photo and recommended Castellan narrow his search to communities around Toronto, where karaoke was popular.

On Dec. 19, Castellan got this posting to the photo.

"i'm katey!!!!!!!!"

That day, as emails were traded, he located the camera's owner, a woman named Heather Irvine.

"Mystery Solved!~ Thanks for tracking us down," she wrote.

And what did she think of Castellan's efforts to find her?

"She was thankful, but I think she was more surprised, and really blown out that the camera was found, that the photos were OK and that someone took the time to track her down," said Castellan, who mailed Irvine the camera card.

And his thoughts on being a sleuth?

"It feels great to finally track you crazy kids down," he wrote on the Facebook site, "but now i feel kinda lost — i need another mystery to solve scooby."