The black Labrador-whippet cross left her Montreal home in the summer of 2010 and was only spotted in British Columbia nearly a year later.
"We just want to know how my dog did this," 28-year-old Isabelle Robitaille said in a telephone interview.
"We don't want to accuse anybody of stealing our dog. It's not like that. We got her, we don't care."
A cross-country odyssey seemed an unlikely fate for a dog who had spent the past five years frolicking contentedly with Robitaille, her husband and three young children.
Robitaille said Pollux was quick to pick up on the prevailing moods in the household and seemed equally happy comforting her mistress after kidney treatment or romping with the kids when spirits ran high.
That all changed on June 20, 2010, when an absent-minded construction worker left a gate open.
Pollux shot out the back and, so it seemed, into thin air.
The Robitailles canvassed the neighbourhood in search of their pet, but turned up no leads.
Pollux's disappearance was upsetting for her adult owners, but proved traumatic for the children, Robitaille said.
"They didn't want to see a dog anymore. Even my parents' dog," she said. "No. They were hating dogs."
The Robitailles eventually resigned themselves to life without Pollux and even acquired a new canine companion from a local animal shelter to help fill the void.
The dog they believed to be dead, however, was alive and well on the opposite coast.
Robitaille's detective work has placed Pollux in the forests around Kamloops, B.C., as late as May, when a local couple observed the intrepid pup drinking water from a nearby lake.
The couple kept an eye on her for a few weeks before bringing her home with them and offering her a temporary haven until space became available at the SPCA shelter.
When she was transferred there in late June, a quick scan of the microchip implanted between her shoulderblades revealed her true identity.
The shelter contacted Robitaille on Canada Day bearing news she could scarcely believe.
"The first thing I said is, 'send me pictures. I don't want to tell you you're a liar, but I don't believe you,'" Robitaille said.
"More than a year later, what do you think, not only your dog is alive but it's at the other side of the country? It's unbelievable."
Unbelievable, perhaps, but confirmed beyond a doubt by photos of a dog who had nothing more to show for her year away than a couple of missing teeth.
A week later, Pollux was home with her adoring family after the international arm of the SPCA volunteered to cover her $1,000 travel costs to Montreal.
She resumed her old routines as if she'd never been gone, Robitaille said, adding she even recalled the individual tricks she'd mastered to ingratiate herself with each member of the family.
Robitaille said her joyous children can't get enough of their four-legged friend, but have stern warnings for all visitors who come to the house — "close the gate!"