Accused of shoes being worn when they weren't worn

I bought my step daughter a pair of boots. They where to small. Went to exchange them and the cashier is arguing with me that the shoes have been worn. I mean she literally just put the shoes on and her toes where in the front of the boots. Now I'm sitting with a pair of boots she can't use and I new pair we bought as she wanted a pair of boots. That is one pep store that will never see me again.