If my 15 year old son was arrested for theft of a auto vehicle they sent him a hearing date but he missed it, what will happen now?

My heartfelt sypmpathy to you for the legal problem your family is facing.  Due to the seriousness of the situation you described, I urge you to seek counsel of an attorney immediately.  In my legal practice I often will assist parents of teenagers who are trouble with the law and I often assist people who are facing legal problems of an emergency nature.  My law firm may be phoned until 8 p.m. each and every day of the year.