No call no show on my record!

When I switched to nights at work I went over the new schedule with my nurse manager. I even wrote it all down. And re-checked what I wrote with her and she agreed that was right! Well, oneday I show up for work, and look at the schedule and next to my name they wrote "No call, No show" for a day I wasnt told I was to work. I was angry, and wrote a note to my nurse manager. When she got back to me she claimed that I KNEW i was suppose to work that day! And therefore it's going on my work record! I kinda argued with her, but in the end just gave in I mean she is the boss so she believes she didnt make a mistake in telling me what days to work! How long will that stay on my record? I'm so fed up with this job. It's like I get in trouble for things I didnt do. Also, the reason why they didnt call me to come in is because my number was not in the book. I went ahead and put my number down. Just in case this doesnt happen again.