I think this is unfair... my TAKS test by be vioded...?

TAKS test are test the state of Texas makes every grade level take. You are not allowed to have cell phones out while you are taking the test. I was sick yesterday when we took, but I came to school anyway. After I finished I asked if I could go to the nurse, and my monitor said to just get some water, and wouldn't let me go. So I went to the bathroom and texted my mom to come get me. She did and this morning I was called into the principals office because they said that knew I had texted my mom. They said my test may be voided. can they do this? They have no proof that I did text her, I was in the bathroom when I did, I had finished my test, AND I wasn't allowed to go to the nurse. I need help in knowing if I can fight this.