The only time I've seen "This shout is unavailable." is because the user deleted/deactivated their profile, therefore their shouts are gone as well.
Truth be told, I don't know what happens to a shout after it's been reported. I'd assume swearing is fine within shouts (I've done it, other members have as well), unless you are directing it at someone with the intention of abuse and/or bullying.
When a user deletes their account, we replace all of their comments with "This shout is unavailable".