Exam Illness A Level

I missed an AQA Chemistry Unit 1 exam on Friday 23rd May due to illness. I had suffered from food poisoning and obtained a letter from my local GP which explained my illness which prevented me from sitting the exam.
My school's examination officer wasn't in on the day so I have not been able to speak to him and I am terribly worried with what grade I will now be given come results day. Now that there are no more January examinations, what will happen to my exam grade for Chemistry? Will it be based on my mock/ other module results in the subject? I am terribly worried and I want to do medicine so can't afford any poor grades. I feel sick with worry now.