This has got me worried. My dad is the primary account holder but I am an authorized user on the account. I reserved mine at the Apple store near me and I am away at college so theres no way my dad could pick it up...
I had the same problem.. I have a line on a business plan, and the owner cant make it to the store.
So I called customer service. They just asked for his phone number, called him right away, and asked him if its ok to authorize me (which took 30 seconds).
Simple as that.
Did you do this before you went to the store or while you were there?