I agree with the answer that says not to blame the entire store for one person's attitude. I've had it happen many times at my favorite stores and I just have to think that maybe that person was having a bad day and not to take it personally. It's not an excuse for bad behavior but sometimes people are so caught up in what is going on with them, that they don't think about how they are coming across. The sales person might just have had another run in with another employee, customer, or even a manager and was in a bad mood. She may have a ton of personal problems that are on her mind or like another person said maybe she doesn't make a lot of money there and is not properly motivated.
Whatever the reason, I don't think it is a reason to be rude to someone but it happens and you just have to not let it bother you and don't blame the entire store for it. Maybe see if another employee is available?
You should definitely let the store know about it though. I usually will fill out a comment card or get on the company's website to send feedback. I do this for good and bad service so people can be rewarded when they deserve it and reprimanded or trained when they are not. I think a company / store deserves to know how their employees are representing them.
If everyone was friendly to each other and people enjoyed their jobs (and were just greatful they had one) this world would be a nicer place. We can all just hope.