Bad Attitude of Sales Staff

I went to buy a pair of shoes at the store that were on display, they didn't have my size so i asked them if i could buy the pair that was on show on the mannequin, the sales lady told me that to take the shoes off the mannequin would be too much of an effort, and i could come back the following day, i slide the one shoe off the mannequin with no effort at all, to which the ladies response was that i couldn't leave the mannequin with no shoes and had to redress her, i got a size 3, to which she rep**** that it wouldn't fit, i then went and got a size 58 and started to slide the first shoe back on, finally the lady told me to leave it and i could go and pay. This happened at 6:40 and the store only closed at 7:00. Is it company policy to not sell a shoe if the mannequin is wearing it and it is the last size?