Relax. Take a deep breath. If your PC hasn't asked for any school supplies, they may not need them. They will get their computer today and will be able to email you any requests/needs. Some may have gotten to the NEX before others. Some may have not wanted to stand in line and are asking parents to send things. Classes start Wednesday. I know that some of the requests I got were after classes had started - like a binder for KP100. But as I pointed out in another post, they were in transition between the old ship's store and the NEX at the beginning of the year last year. Supplies should be easier to get this year.
Your PC will not get in trouble because they are short a notebook right now! If they are mastering the skill of interacting with upperclassmen in a friendly manner without crossing the line into being too familiar (otherwise known as frat) the upperclassmen will help them. They may be lucky and have someone pick something up for them at CVS or Target. Bottom line - don't panic. They'll be fine.