ANOTHER PERSPECTIVE:
I once went with my friend to the ice cream store (before i got married) and when we got back to her car she couldnt get it to start. We called Chaveirim and they sent a guy down, we showed him the car, apparently the steering wheel was locked, he got the car to start. We thanked him and he left. The next day my friend sent a check to chaveirim, mentioned the story and that was it! The guy didnt call her to say thank you, for her thank you. That would have been absurd! We didnt think of small talk with the boy while he was fixing the car either! We didnt call to thank him personally. The Hakoras Hatov was there, but in a very modest way. What is this with boys and girls that are so friendly and comfortable with opposite genders. I think it is the Yetzer harah, and he is laughing!