It's a misunderstanding on DD's part and on the school's part. None of them knew that DD's father had taken the money for safekeeping (the irony).
By all means go into the school to explain the situation, just so that DD can stop worrying.
You can't really blame the school for anything because it was your DD who told them the money had gone. The key thing is to say that all is well and you are sorry for the confusion.