How to make an inquiry when your child’s belongings are missing
In this case, you are making an inquiry because you cannot find your child’s belongings.
It is polite to express gratitude when you borrow something belonging to the school. If it is washable, please be sure to wash it before returning it. It is best to use polite Japanese when you ask a schoolteacher to look for something for you since it will be extra work for the teacher. You may personally thank the teacher the next time you see him/her.
Model
Conversational flow and useful expressions
Greeting
What your child borrowed
Gratitude
What you cannot find
Asking if it is at school
Closing
Parent's name
Supplement
In a case such as this, when you might be asking for extra work from a schoolteacher, 「お世話様です」(osewa sama desu) is more polite and better than「おはようございます」(ohayo gozaimasu) as the initial greeting.「いつもお世話になっております」(itsumo osewa ni natte orimasu) is an even more polite phrase and can be used when you ask a larger favor of a schoolteacher.
The phrase 「ないようなのですが」(nai yo na no desu ga),「ないのですが」(nai no desu ga) or 「ないみたいなのですが」(nai mitai na no desu ga) is a softer way of saying the blunt「ない」(nai). In the above context, these phrases mean, "I cannot (seem to) find (something)", or "(Something) seems to be missing".
Attaching "~chan" to a girl's name or "~kun" to a boy's name is usually only done when addressing or referring to children besides your own. It is not very common to attach "~chan" or "~kun" to your own child's name, especially in public.