I isn't got the answer but it's written the conversation is closed by experts

Dear Student, 

Such questions are made for enhancing the self-creative skills and should be tried answering on your own. However, here are a few points that will help you in framing your answer:

• I have lost my school diary last week. 
• Despite my best efforts, I am unable to find it. 
• The school diary is the official medium of communication between teachers and parents. 
• It is mandatory to apply leaves and write formal applications through the diary.
• It is therefore requested to issue me a new diary. 

Kindly refer to our website for the format of letter

Regards