'It was a powerful speech that stopped me in my tracks,' recalls the 35-year-old champion swimmer, who's still visibly moved by the event. 'I had a lump in my throat and had to sit down and listen right until the end.'
Sam has good reason to feel emotional about the apology. Her gran Ronnie grew up in a Salvation Army home from the age of nine, apart from her Irish father Thomas and Aboriginal mother Zillah, of the Ngemba tribe in Brewarrina, north-western NSW.
Although Sam believes Ronnie was well looked after at the home, she did endure hard times before she left to make her own way in the world at the age of 15. Once, Ronnie tried to scrub her skin to make it whiter and, even more devastatingly, she lost touch with her parents forever.
'As a mother, I can't imagine the pain of being apart from my children and how that would affect the rest of my life and their lives,' says Sam, who has two sons - Isaac, four, and Lucas, three - with husband Tim Fydler.
Sam and her mum Lin never got to meet Ronnie, whose looks mirror those of her granddaughter. They only discovered their Aboriginal heritage in 2001 after determined research by Lin, who was given up for adoption as a newborn.
Lin finally tracked down the whereabouts of Ronnie, only to learn, in a sad twist, she had died just three weeks earlier.
'Because Mum had always been led to believe we were Italian, it was a complete surprise, and I was unsure how I felt at first,' says Sam, who is one-eighth Aboriginal.
'Back then I didn't have the knowledge or understanding of what that meant, but now it's something I am really proud of.'
That pride ties in perfectly with Sam's new appointment as an ambassador for the Northern Territory, a diverse landscape that resonates with ancient Aboriginal culture.
'As a swimmer competing internationally, I travelled to most countries,' says the two-time Olympian and former breaststroke world record holder who retired from the sport in 2000.
'But even before I became aware of my background, the place I always wanted to visit was the Northern Territory. Like many Australians I put it on the backburner, seeing the world first even though the most amazing destination was right there in my own backyard.'
Just back from a memorable five-day tour of the Northern Territory with Tim, Sam flashes that million-dollar smile as she details some of the highlights.
There was the thrill of feeding pork on a stick to three-metre-long crocs on the Adelaide River, hearing Dreamtime stories while cruising between the rugged sandstone cliffs of mesmerising Katherine Gorge, eating the 'best Thai and Indian meals ever' in cosmopolitan Darwin and farewelling the red heart of Alice Springs as they set off on the famous Ghan.
'It was relaxing on the train watching the scenery change from rich red desert to green,' Sam recalls fondly. 'And we certainly slept well at night because of the constant movement.'
Sam also warily tasted bush oranges and raisins while watching her adventurous husband bite into all kinds of bush tucker.
'Tim ate emu pie, kangaroo and whatever other native food was put in front of him,' she says. 'He had no fear and enjoyed the
Sam adds that Tim has enthusiastically embraced her Aboriginal heritage.
'Tim is just so proud that his sons are part Aboriginal too,' she says. 'Like me, he's eager to learn more about my ancestors,
the Ngemba people. While we were in the Northern Territory he bought a didgeridoo for the boys. He loved the sound of it and
is practising the circle breathing so he can teach them how to play the instrument. That made Mum quite teary when I told her.'