It might not be worth it in time or money for you to go back to the store, but if you have a phone, call the store number on the receipt and let them know what happened.

I've had no problem returning spoiled product or recently, I was charged for 2 of an item, when I only bought one. I call them as soon as I notice the problem, and then when I go to the store they already know the issue and are quick to resolve it. "I'm the lady who called about such-and-such".

Nowadays the grocery stores have computerized registers that give the product name/description as well as the cashier's name.