Sharon Falconer had a silver heart-shaped locket made recently to contain some of her late husband's ashes. It was sent by an Alexandra jeweller to Cromwell to be sealed, and was lost on its way back to Alexandra.
Mrs Falconer said it was sent by track and trace courier post, and was last recorded as being collected from Cromwell on April 21.
No trace of it had been found since, she said.
Mrs Falconer urged anyone who might have found the locket to return it to her.
"If it was stolen or sent to someone else by mistake, then those people probably didn't realise the significance of it. There is a [postal] investigation under way to try to find it.
"I just really want it back. Getting another locket made is not going to solve the feeling that part of my husband is missing," she said.
Mrs Falconer's husband, Adrian, died of cancer on April 5.
His body was cremated, after which Mrs Falconer arranged for some of his ashes to be placed inside the locket.
She hoped someone had found the locket, which could not be opened.
It was on a chain, and had been sent on its own, she said.
"It could have been sent somewhere else ... just in case there's the small chance that someone's come across it, taken it, or received it by mistake, I would love for that person to return it," she said.
