What if my photo was published in a magazine or other copyrighted work?

The overall magazine or other copyrighted work would have copyright protection for the original parts. But your photo would not get registration unless you register it.

“If you have written an article, column, or short story that has been published in a magazine, newspaper, or other periodical, you may make a separate registration for your work. This kind of work is called a ‘contribution to a collective work.’”
— U.S. Copyright Office, FL-104, Reviewed 01/2011