Used to happen to me all the time when I was younger, especially in Saks. I would walk through the front door and instantly turn invisible. And if I did find something I wanted and took it up to the counter to pay for it, I could always count on a disdainful look from the clerk. I used to tell my friends that Saks must have a special training program for its clerks to teach them the right degree of sneer for each customer.
Doesn't happen to me any more since I discovered online shopping.