I'm inclined to agree with Duke. Don't mention it during your interview but if it does come up, apologize and thank the gentleman for taking time out of his busy (be sure to put a little emphasis on busy) schedule to give you directions. As does Duke, I too suggest that you don't sweat it. By now the gentleman has probably forgotten that you called for directions. With all that said, do learn the lesson and become better organized especially as it relates to very important matters.
Good luck, Duma. I'm rooting for you.