The family of a four-year-old missing in the Outback are being targeted by cruel trolls spreading conspiracy theories with a friend demanding they stop.

August 'Gus' Lamont was last seen playing in a mound of dirt near his grandparents' homestead on a sheep station 40km south of Yunta last Saturday, September 27.

Fleur Tiver, 66, said the tight-knit community in eastern South Australia still hopes Gus is hiding on the property.

Her ancestors have lived on a station alongside the Lamonts since the late 1800s.

News of Gus's disappearance prompted Ms Tiver to leave her home in the Adelaide Hills and return to the rural area to assist in the search.