I too was 'told' I was up-to-date, and lost a ton of parade pictures of the family from this morning. Badly done, Apple. Badly done.
So just download a "production" iOS 7 IPSW and "update" to it.
That's what I did to update when the iOS 7 GM came out, and I've used it in the past when I unintentionally let an iOS 6 beta expire.
[1] http://www.jailbreaksquad.com/wp-content/uploads/2013/01/Bro...