As a judge in contests at the Butch O'Hare contest, a missing mirror should not cause any issue one way or the other. The point is to judge on technique and skill, not on the historic accuracy of the model or the amount of after market items added. Bottom line, depending on the Hurricane you are modeling, there may not have been a mirror. I cannot speak for judges everywhere, but that is how its done where I am. I wouldn't worry about it, or if you want to include it, scratch something together and make it look right. either way should be fine.
John