Whether the writer of the text is anonymous or not should have no effect on these issues. The writer holds the copyright unless it is a work made for hire.
Writer owns the copyright forever no matter what. Even if you made smth for hire, you still owns the copyright. Copyright is smth you can't sell, can't buy, can't lose. "Copyright by John Smith" means exactly: "John Smith has made this". It's just to state the fact.
Regards, Talthen