What is FDB proticol (sp?) on the following situation?

Go to a restaurant craving a roast beef poboy, and after scanningthe menu iI ddecided that's what I would get. After I ordered and my food comes out it's a brisket sandwich. I tried thinking about what I actually said when I ordered but it was so subconscious that I couldn't remember what I actually said. Giving them the benefit of the doubt, I decided to just eat what I was served but it's pretty terrible... So do I just order again and pay for both? Pretty shitty situation but I am unsure if they fricked up my order or if I had a brain fart