They'd last clapped eyed on him 10 years before and 1800 kilometres away when he stormed out of the home they shared in suburban Melbourne.

He was, they believe, Ms Gillette's long-lost former partner - and the father her boys barely knew.

They'd last seen Russell Jenkin in September 2006 when, after a fight with Ms Gillette over Friday night football, he walked out of the family home in Werribee, leaving his two sons - aged four and two - behind.

Despite countless appeals for help to find Mr Jenkin in the decade since, the children, Ethan and Charlie, do not know what happened to their dad.

That was until January this year.

While on a trip to Queensland with his mother, Ethan, now aged 15, spotted Mr Jenkin inside a shopping centre car park.

"We were coming out of the shopping mall and he was coming towards us, casual-like, we then got into the car," Ms Gillette said.

"We drove past him and he was observing us, and he took his sunglasses off and I thought, that's definitely him.

"It was a bit numbing ... realising it was him. We could have approached him, but he could have approached us."

That sighting was on January 27, at Caloundra Stockland shopping centre on the Sunshine Coast.

Ms Gillette, who now lives in NSW, had taken her two boys, Ethan and 12-year-old Charlie, to Queensland to visit her older daughter - the boys' half-sister - who lived nearby.