Was it a gallon jug? Just kidding! No worries! As the above poster said, take care of yourself from here on in and you will be fine. I was in the same predicament when I was pregnant with my first and he was born very healthy.
most people don't realize that they are preggo until way past there period is due. The only people who are chronic testers are ones who are trying to concieve. Believe me, the majority of babies are not here because of people trying. My point is, you know that your preggo now, so take your prenatal vit. and I am sure that one night of drinking isn't going to affect your pregnancy or your baby. I am sure that your Dr. would even reassure you about this if you brought it up.