ACS will send you a letter when their investigation is complete informing you whether or not the allegations were founded. It is unlikely you will be able to find out who made the report as hotline calls are supposed to be anonymous.
You will receive a letter that will advise you of the outcome of the investigation. Hotline reports are anonymous so, like Ms. Bovee said, its unlikely you'll find that part out.
This advice is not meant to create an attorney-client relationship and is a general answer to the question posed.