Did you bring my bag?

The cashier said, “Did you bring my bag?” as I was waiting for him to ring up my Ebisu beer. I did not bring his bag but did not say that because if I did, he would have thought I was insane - I'm sure of it. 

For those who wonder about his question, it is the store's new code to encourage its customers to bring their own shopping bags. If they did, the store will deduct a percentage from the shopping bills; a green tactic to reduce the use of plastic bags. 

When he said "my" bag, I was giving him a mental lecture that "the personal pronoun of 'my' is used by the person who is speaking and the correct word is 'your.'"He did not hear it because he was not making mistakes in English - I think. In fact, he said it to me in Japanese, "My bag wa motte imasuka?"

I said yes and he charged ¥1,117 for my six pack, instead of the regular ¥1,120.