If your story has been archived (moved offline), you can go to your story, and click on Unarchive in the Author Options box.
This will remove it from archive temporarily, or for a week or so.
Please note your story will go back to archive after a while, but this way, you will always be able to take a look at your story through CC, even though it's been archived.
If you are not the author of the story you wish to look at and its been archived, you will have to contact the story's author and request that he/she upload the story back up to CC. This is done by using the form supplied when you attempt to view an archived story or one of its critiques.
Archived stories are not visible in the "Older Stories" list of the Story Queue, but you will be able to view them through the "Everything" list.