You must have accidentally overwrote the post because the permalink of the draft is http://happymotherdiary.wordpress.com/2011/09/23/baby-shower.
There is still revision of the original post so you can retrive the content and publish a post with it. And then you can change the publishing date.
1. Go to edit the draft, "St. Valentine's Day" and find "Revisions" panel. If you don't see it immediately, Check if it's checked in the "Screen Options" on the right top on the page.
2. Click the revision right before you overwrote the content (29 October, 2011 @ 15:28) and copy the content and paste it to a new post.
Optionally you can edit the permilink for the "St. Valentine's Day" to something else in order to make the permalink of the restored post to be http://happymotherdiary.wordpress.com/2011/09/23/baby-shower
Hope it helps!