Members past and present attended a thanksgiving service at Quorn Uniting Church to mark 140 years since the laying of the original foundation stone.
"Unfortunately that memorial tablet seems lost," said visiting speaker David d'Lima, of FamilyVoice Australia, after the event on November 24.
"No photograph of the stone is featured even in the 1980 centenary history of the congregation. It is time for a rebuild, not so much of the architecture, but of the people who are the church."
Mr d'Lima encouraged recognition of the foundational theme in Australia's Constitution that declares the people "humbly relying on the blessing of Almighty God".
He said it had been 20 years since that declaration in the constitutional preamble had been effectively ratified again by voters.
Mr d'Lima commended the Port Augusta Uniting Church for helping to fund a work to educate children in the Quorn district under the links between the two congregations.