As a mod of Education & Careers I have to say that honesty is the best policy and that you should have asked off through proper channels at least two or three weeks ago.
As a regular guy I have to say that in my early twenties I once called work before my shift and told them I had explosive diarrhea. I acted ill and was abrupt and got off the phone as fast as I could. One would normally not see a doc for falling victim to the dreaded Green Apple Quickstep and they didn't ask for a doctor's note. All that trouble and I don't remember a damn thing about the show.
I do not condone lying to management and I currently have such a job that I try to be very careful in planning days off ahead of time. IOW if you try this and it backfires then tough shit, can't say I didn't warn you :D