Royce Player used to be neighbours with the family and is also an experienced tracker who knows the area well.
"I would've thought they might've found him by now, you never know, this could be something someone's missed somewhere," he said.
"Under a bit of bush, a bloody hole in the ground, or an old motorcar … could be anywhere."
He said it could be easy to "miss a little four-year-old" if the searchers were spaced out even "20 metres apart".
Mr Player, like many of the volunteers assisting in the extensive search efforts, said he dropped everything to come and help with the search for a lost little boy who "wants his mum".
"I'm a parent, so yeah … well, I don't know what it would be like, but I wouldn't like to go through it myself," he said.
He said the conditions were challenging, especially overnight, with temperatures dropping below 10 degrees Celsius.
"It's not that cold now, thankfully, but … you know it gets a bloody hell of a lot colder than this," he said........................
But, police said the print might be from before Saturday.
"We've got to remember that he [Gus] actually lives on the property and that might have been a footprint that he might have left there a couple of days ago, even before he went missing," said the officer in charge of the Yorke and Mid North region, Superintendent Mark Syrus.
While the print was found near a road, Superintendent Syrus said he thought it was "highly unlikely" anyone else was involved in Gus's disappearance.
The search for missing four-year-old Gus has entered its seventh day, with no new signs of the boy.
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