I think my intial reaction would have been to hammer to get away, my next thought would be to find a safe place to stop and get off my bike. That is rude to just draft off someone.

As far as the other poster, I would have stayed in their draft to, if they know you are there and not trying to get away they must not mind. I still may have asked though. I don't know I've been know to ask in a race if someone down like I am happens to want to work with me. The only time I just draft is off my team, or the peleton.