Or...?

I was ordering a meal at the food court in a mall, and the cashier said: "Would you like regular coke or diet coke?"
The place being very crowded and noisy I didn't hear her question properly so I was like: "Okay!" The lady had to repeat her question, and being my always-so-blunt-self I replied and told her whatever it was that I wanted.

I don't know if you've noticed it, but from my side it was merely a mistake of not hearing the question well. However, a lot of times it happens that you ask someone a question that has 'or' in it, they'd be like Yes, or okay, and what are you supposed to take from it?
I remembered it having watched Anne and the King, and she asked him a question with the word 'or' in it and he merely replied by saying 'Yes'. It was obvious he was teasing her but it happens a lot in life, and I simply get an affirmative to a question that requires from a person to choose one of the two things I stated in my question.

It is somehow a bit funny though.