Her husband Bob told the Herald that the family could not rest until Mrs Stewart's body was found.
"It's an enormous insult to her and our daughters that she is out there somewhere unknown, when she shouldn't be," he said.
Mr Stewart, now 80, says it never gets easier coping without his best mate. "The hardest thing is the loss of a person you valued so much.
"Even now, little things creep back into your memory and just bring tears to your eyes immediately.
"It doesn't go away, I don't know if it ever will."
Today Mr Stewart and Detective Senior Sergeant Mike Sears, the officer in charge of the investigation into the 2005 disappearance, retrace Mrs Stewart's last steps and reveal what they think happened to the grandmother of three and how the public can still help.
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