How do you figure you should dispute your charge for groceries? YOU paid for them. Just because you let them does not mean that you didn't pay for them. You are supposed to dispute fraudulent charges. I hope your card company finds out you lied to them and the store is probably going to tell them it was a legit purchase.
You do realize that they constantly hear stories like yours "It was an accident. I forgot I put that in my pocket." Yes you could be charged over that incident.

