Wrong pricing

I went to the Woodmead woolworths to purchase a few items, there was a dress that was in the sale items but not marked down, I went to the till and asked the lady to check if it was marked down and she said no, I a few minutes later a few other items that I did buy was charged at normal price. I then asked her if she was sure that the dress was not marked down and she looked confused. She did not bother to even check. Now I look online and the dress was in deed marked down. What kind of a dumb system is this that they don't even know what items are on sale. Now I cant purchase the dress cause it is sold out in my size.