"Considering the implications of finding something like that, in an end product that's supposed to be checked and that they stated was washed three times and checked at every stage, there's got to be something wrong there."
Mr Harris said he contacted Pam's and was initially offered a $15 voucher. "When I said that was still not good enough, they upped it to $50."
He declined the offer.
Mr Harris said he would not buy Pam's salad again.
A Foodstuffs spokeswoman said the company "sincerely apologised to our customer for any upset caused".
She said Foodstuffs had been in contact with the customer regarding the issue and took any incidence of foreign matter in its products extremely seriously.
"In addition, our supplier has a risk-management plan in place to minimise the risk of this occurring."
"A full investigation with the supplier has commenced and they are currently working through this process," she said.