Mrs Nicholson said the walking stick had been stained a darker colour, some paua had been removed and some spots were sanded flat.
She had not expected the walking stick to be returned, she said.
"Those things don't come back and I just wonder where has it been.
"Some people think it's kids that took it but I don't think so. Their conscience has pricked them, something has happened," she said.
"When I first saw it I thought 'no', but that's not because they have darkened it - they have tried to alter it - they have rubbed some of the things off it, maybe to re-sell it."
Mrs Nicholson's son, John, was going to re-varnish the walking stick before it was returned to the headstone, she said.
"They have had a good go at it. They have taken the paua off some of it so they are really mongrels, but never mind, I am not complaining.
"We have got it back and that's the main thing. It just has to go back to where it belongs, those kind of things can't go to anybody else," she said.
Mrs Nicholson was not worried about the walking stick being stolen again.
"I don't think it will get stolen again, I think it was just a one-off."
The greenstone waka stolen from a headstone at Kauae Cemetery in December was anonymously returned to the same headstone it was stolen from less than two weeks ago.