The urn had recently been renovated, and was a clean white and not blackened like a similar urn at a nearby grave.
"It was beautiful and white, a beautiful thing."
Granddaugher Heather Robottom said Stonehaven had carried out the renovations.
Stonehaven staff told the family the urn was very heavy and would not have been easy to remove.
George Stanley Grantham was 42 when he died in a sawmill accident near Matawai in 1942. He suffered a horrific death, Michael Robottom said. Mr Grantham's wife Sarah Anne died in 1978, aged 77.
Heather Robottom said her mother was upset at the violation of her parents' grave. She and her 93-year-old sister are the only surviving children of George and Sarah, and all the family asks is for the urn to be returned.
- The Gisborne Herald