Advice on Bus Mistake

My son is 6, nonverbal, and level 2. He has an active IEP in place and on the first day of school he was put on a bus home by mistake, he is a car rider. The most frustrating part if this is there were several communications that he was a car rider, some as early as 9AM that morning. We pulled him from school until the case meeting this afternoon. This was a mistake both on the administrative and the teacher's part. We are headed into a case meeting this afternoon to address what happened and have him transfered to a different school as the trust is broken with the teacher/school. What questions should I ask or what advice might you have? I am honestly still in shock.