Some people are rude or unpleasant or negative or whatever. But I suspect they're like that regardless of where you shop or what you're wearing.
I'm with leelee and swanky. The salesperson was probably having a bad day and would have taken it out on you no matter what you were wearing. She probably didn't even notice. Remember, you said the store was kind of in disarray, and it's the SAs who have to clean all that up. I think they probably spend most of their time doing stuff like that because people come in with the attitude that it's discount, they don't need to treat the merchandise with respect. I'd have a rough time working there too (though hopefully wouldn't take it out on the customers.)