My child was lost during a field trip.

Hi, everyone. I am trying to find information regarding policy about field trips. We found out home from a notice of a teacher that our 1 grader was lost during field trip. We asked a child about it, we called in a museum about more information regarding this. Thank God, a worker found him, and he returned to his group safely. But it makes us, parents, wonder what is a policy regarding those accidents? does anybody have an experience like this with school? Thank you for all comments.