Warning: Unattended Children at Parks and Rec Day Camp

My child was left unattended at a Parks and Rec day camp by the teacher. 
I recently signed my daughter up for a Shelby Twp. Parks and Recreation class. The class runs from 10-12 at the band shell. Today, I was slightly late due to traffic back up on 24 mile road. According to my phone, it was only 12:01 when I pulled into the parking lot. I arrived and did not see the instructor, nor my child in sight. I found my 7 year old down on the lawn, playing with another little girl whose babysitter was present.  I did not know the girl, nor the babysitter, that my daughter was playing with.  I asked another parent where the teacher was, and the parent informed me that several minutes prior, the instructor announced that she was leaving because she “had another job to get to.” My understanding is that there was no effort to make sure each child was even with a parent, or that each child was with the correct adult.  This other parent had stayed to keep an eye on another little girl that she knew, because that child’s parent had not arrived yet, and she did not want to leave her unattended. There were other children that were picked up between the instructor’s departure and my arrival. At minimum, I can verify two children who were left unattended by this instructor. I was very fortunate that a couple of people had stayed, and I was very lucky that these were good people. Again, the class was scheduled to end at 12. I was only a minute, possibly two, late at the most. I have no idea how early this instructor left, or how long my child was unattended. I left my home reasonably early to get there, unfortunately, with all of the construction, traffic and timing are difficult to predict. I shudder to think what could have happened had I arrived any later. I called the Parks and Recreation Department and repeatedly asked to speak with the director, but was told “he was somewhere in the building” and I could have his voicemail. Then I was told I could speak with “Mark” who was responsible for setting up the classes. I spoke with “Mark,” who listened to me, and was very apologetic, but repeatedly informed me that the classes were subcontracted, and it was the instructor’s responsibility to make sure the kids were sent home. He offered to “speak with the instructor” to “make sure it didn’t happen again.” I stated that I didn’t feel he was taking the situation seriously, and he asked me what I would like him to do. I was told all he could do was speak with the instructor, and sometimes “younger people make bad decisions.” I asked why there wasn’t a general policy in place for drop off and dismissal for all of the classes, that the subcontractors had to follow. I pointed out that the Nature Center uses a sign-in/sign-out policy and checks I.D’s, as does the day camp my daughter attends through UCS. I was told they would “take it into consideration.”   First, I am incredibly disappointed in the lack of concern or willingness to take responsibility by the Parks and Recreation Department. Second, regardless of whether or not the class was subcontracted, it was offered through the Parks and Recreation Department. I was not informed at any time that the class I was signing up for was subcontracted.  I signed up and paid for it through the Parks and Rec department, and did not, at any time, sign a waiver absolving them of any responsibility should harm come to my child. While the instructor is immediately at fault, it is Parks and Recreation that is, ultimately, responsible for the well being and safety of my child. Today, the lack of oversight, proper policy, and effective management failed my child and other children. What happened today was child endangerment. I guarantee that, as a parent, had I left my 7 year old daughter to wander a public place while I left the premises, I would have been charged with something.
Why are there no rules or policies in place to prevent something like this from happening? Is there verification that they are trained in the classes or camps that they are running?  Do the instructors and their staff have to go through a background check? Lastly, why is there no universal policy in place to ensure that the children are safely dismissed from these classes? From now on, my children will be attending the camps and classes through Rochester's RARA, where they are actually responsible. I would rather pay a higher price and a non-resident fee and know my children are being looked after.