This is the email I sent. Please let me know what you think.
Dear Mr. TEACHER,
My daughter, SUPERSTARSTUDENT, has told me that some items have been going missing from her lunch box for the past two days. She's been putting her lunchbox in her locker every morning and by lunch time, things seem to be going missing. The items that are going missing are her chips and her dessert (starbursts). DD brought this to my attention yesterday, the 18th. Apparently, the same items went missing again today, the 19th. Her sandwich, fruit, string cheese and drink seem to be safe.
I know we discussed the possible candy bar going missing issue a few weeks ago. I wonder if you are aware of any other students that may be having a problem like this?
Since this has become an issue for DD, I was wondering if you could point me in the right direction of who to speak to regarding this issue. Please feel free to contact me at #### or by email to discuss this.
I hope you don't mind that I cc'd Mr. PRINCIPAL. I just wanted to keep the administration in the loop, as well. I look forward to hearing from you and thank you very much for your help!