I know someone just like that. I just walk away and let her handle the situation. I figure it's one less thing I have to worry about.
Definitely know PEOPLE like this for sure. But yep, I stopped getting mad about it or feeling some kind of way when they thanked the other person and totally acted like I never initially tried to help them in the first place. Because as I look at it, if the other person gave them the wrong info, or if it was an order that had gotten a mistake on it. It wasn't my buns in the fire.