The Bedford women found the plaque missing from their mother Joan Gattorna’s grave in Acacia Court when they visited on Good Friday.
Their father’s plaque on the adjacent plot was still there.
‘It’s a bit of a mystery as the plaque is of no use to anyone,’ Jill said. ‘It’s a bit sad that it’s gone because it has brought it all back.
‘Our father died in 2006, our brother in 2007 and our mum in 2008 so there’s a trio of remembering things.
‘There will be no questions asked if it is returned.’
Metropolitan Cemeteries Board marketing manager Andrew Fox said the disappearance of plaques was very rare.
‘Replacement (of a missing plaque) is the family’s responsibility,’ he said.
‘If a plaque is damaged, such as by lawn mowers, the board will contact the family and have it replaced.’