Question

A teacher of a class in Paris organized a flight to Israel for his entire class. They arrived at the airport, and then he discovered that he did not have his passport with him. There was no one at his home who could bring it to him, and he had no way to return home himself. Well, in the end everyone missed the flight.
 
Is he obligated to refund the money for the flight tickets to the parents of the children in the class? What is the law if he simply forgot his passport? And what about a case where he did not forget it, but an unavoidable mishap occurred—for example, he took a passport that he thought was his, and it turned out to be his wife’s passport?