In formal writing, the inserted word or phrase is supposed to be enclosed in square brackets to indicate that it is not the original source speaking: "he wanted to go to [the] circus".
The slightly more obnoxious "sic" can be used when you want to leave the grammatical error in, indicating that the error is in the original source: "he wanted to go to circus [sic]".
"Being misquoted" usually implies that the semantic meaning of what was written is different from what was said. It does not usually mean articles and transitive words were added.
The slightly more obnoxious "sic" can be used when you want to leave the grammatical error in, indicating that the error is in the original source: "he wanted to go to circus [sic]".
http://en.wikipedia.org/wiki/Sic
A good journalist will adapt their own language to make the unmodified quote fit in where possible. Being misquoted is a sign of sloppy journalism.