STAFF CAN'T COUNT TO 3

We often visit McDonalds Ellis Park for breakfast as it is on our way to work. My husband always ordered an extra hashbrown. 9 out of 10 times it is missing. We keep having the same argument with staff who insists the hasbrown is in when you explain but I ordered 2 meals and a extra hasbrown so there should be 3 ..... then we are told please move forward we will bring it to you. Sure we have the worlds time available that is why we bothered to use the drive-thru and not in-store. How difficult can it be?