Hello Nicole and arualis. When sewing this dress for the “Above All Fabric Sew A Long” http://www.aboveallfabric.com/blog/?page_id=5093, I remember the facing seemed much too short, but it’s because you will be sewing the short ends of the hem facing first, at the unfolded back edges/placket and then sewing along the longer hem edge after http://sarahbdesigns.net/images/SBM_SewAlong_41.JPG
When you turn the hem to the inside, the back edges/placket will be refolded to the inside, the facing will fit. But do check if your middle piece was cut correctly too.
This picture from the Sew a long Flickr group show the finished hem http://www.flickr.com/photos/77893210@N00/5862792212/in/pool-1658614@N24
I hope this makes sense, and that you get the dress finished.