I skipped my class and I don't want to go to detention?

I skipped world civilization during 4th period on Monday and I don't want to get a detention. I told my teacher that I was at the nurse but she went to her and asked her if I was there and she told my teacher that I wasn't there. I claimed that I was there even though I was in the cafeteria doing my project due that day instead. And I RARELY ever skip. That was the one and only time I did it. What can I do to get passed a detention? She said I could bring a note. Can I say something to the nurse to convince I was really there even though I wasn't?