I was in childcare for 3 1/2 years. That is just not normal.
First of all, for the other mom to not know what you were talking about is odd. How did you know which child your son bit? It's against the law for the teacher to give ANY names. (At least here in TX it is.)
Second, if they had been having behavior issues for 2 weeks, it should have been discussed with you. Periodic time outs are not enough to bring up with parents. Just about every child end up in time out. It's part of how they learn good behavior. I can see how he might get time out, but still get a good report that day. No teacher wants to see a child get in trouble with mom if they corrected their behavior.
If they are refraining from telling you about it because they are treating him like a "special needs" child, that's a whole different issue. Sometimes, teachers get in a frame of mind that the child is "just that way" & treats them accordingly.
Then, there's the lack of communication from the director. Oh boy.
One of things that I've learned in my current job is that just because a childcare center is in a church, doesn't mean it's better. Some of the best centers I've seen have been in churches, but so have some of the worst. (I'm a preschool photographer, and go to a different center everyday.)
If the teachers are treating your son differently because of his sensory challenges, it might be time to look elsewhere. I agree with you that he shouldn't be at a "special" school.
Good luck & good job being proactive!