GILLIAN Rodgers, 74, found the tightly-packed bag of white powder, about the size of a packet of cigarettes, on Saturday as she packed for a trip to Blenheim.
She took the bag to her local police station and was told it was 55g of amphetamine.
She says she last used the suitcase four years ago on a month-long cruise around Australia before flying home from Sydney.
The pocket where the drugs were found was the only one which wasn’t padlocked, she told the NZ Herald.
Ms Rodgers was shocked to discover she was being used as a drug mule.
“I wonder if they were going to try to retrieve it. I’m sure they would have wanted it back. I wonder if they followed me,” she told the paper.
“I could’ve been picked up at the airport. Or if I’d gone through somewhere like Bali or Thailand with that in my bag… terrifying.”
Customs spokeswoman Nicky Elliott says the drugs could have been planted anytime since Ms Rodgers last used the suitcase.
Customs processed about 10 million travellers a year.
“We are confident this system works well and that the border is fully protected.”
Police are now looking into how the drugs may have been planted in the suitcase.