English in Real Life

I was wanting to use the car which my brother Josh had taken. So I went to my brother Eric and experienced the following exchange:

Me: Do you know when Josh is getting home?
Eric: I do
We stared at each other.
Me: Can you tell me when Josh gets home?
Eric: I can.
We stared again.
Me: Are you trying to get punched in the mouth.
He looked at me in confusion.
Me: Tell me when Josh is getting home.
Eric: I don’t know.

Now what happened, I think, was that Eric meant to say “I do not”, but dropped off the negative. But what’s really funny is that he experienced the same conversation this way.

Me: Do you know when Josh is getting home?
Eric: I do not.
Me: Can you tell me when Josh gets home?
Eric: I can.
Me: Are you trying to get punched in the mouth.
He looked at me in confusion.
Me: Tell me when Josh is getting home.
Eric: I don’t know.

I love English.