It is up to the 16 year old's parents who they date. Your friend is exhibiting pedophilia behavior.

By bringing it to a mechanic...................

Who is he? This is a Q&A Forum. You have not asked a question.

You can call the cops, who will do nothing. IMO you will lose any lawsuit.

You are entitled to a refund, but that's it.

This is a Q&A Forum. You have not asked a question.

Please realize that we have no idea what you are really asking.

Stores are allowed to detain you if they suspect you of stealing. If they are charged, they need an attorney to defend them.

You can take all the paperwork to a local attorney to advise you on the likelihood of success.

Take all of your information to animal control. Consider getting a restraining order.