How would you add a header when using the mt3-gettysburg template?

I went to view my blog the other day and was given a 404 error, so I looked at the FTP, and the serendipity folder was still in there, but the name of it was changed to 'serendipity.need_to_update' and I can no longer access the folder or anything in it.

I can't back it up because the folder will ...