"I knew she hadn't come inside, and, you know, your heart just drops," she said.
A frantic search began. Neighbours, emergency services and the wider Oamaru community scoured nearby properties and the Oamaru Old Cemetery across the road.
"Wherever she'd gone, she'd gone quick — and there was just no sign of her," she said.
"It was the silence. We couldn't hear her. We couldn't hear anything. We were calling and calling and calling and calling."
When brothers Wiremu and Hunter Ball and Jax Carey saw people searching for Phoenix at Fenwick School, near their house, they dropped everything to help.
"We searched the whole [Oamaru Old] Cemetery," Jax said.
After looking for Phoenix for about half an hour, they heard crying, and thought it came from the nearby Oamaru Lawn Cemetery.
But they could not see Phoenix anywhere.
"We were just walking back home, and we heard her again," Hunter said.
This time, they found her.
"She was standing in an old, kind of abandoned-looking, place, just crying," Wiremu said.
They were relieved to have found her — and she was happy to see them, after being lost for about two hours.
"She just said 'yay', like she knew who it was," Hunter said.
The three boys, who knew Phoenix and her family, comforted her and called out to other searchers.
They returned to visit the family later that day, to make sure they were all right.
"They're just the kindest, most mature, tenacious, incredible young men — they deserve to understand the magnitude of what they did for us," Gilmour said.
"That day could've gone so much worse."
In the darkness of the situation, the Oamaru community's light shone, she said.
"I came out to the whole community there [helping to search], and I couldn't believe it.
"It was a real sober reality of what was going on, but at the same time, knowing that everyone was there helping us was just amazing.
"Oamaru's just incredible. We moved here a couple of years ago for a better place to raise our babies and we are just so glad we did."