I've just set up an S3 bucket and have a transform in my template. Should these transformed images be saved on S3? It doesn't look like they are, however my template is pulling out an S3 URL:
<img src="{{ asset.getUrl(resize) }}" width="{{ asset.getWidth(resize) }}" height="{{ asset.getHeight(resize) }}" alt="A photograph of {{ entry.title }}" class="grayscale grayscale-fade wp-post-image ral-mugshot">
When using a base image at http://s3-eu-west-1.amazonaws.com/rallyagency/princess-leia-princess-leia-walking-in-new-york-is-just-plain-awesome.jpeg, my template outputs this:
<img src="http://s3-eu-west-1.amazonaws.com/rallyagency/_200x200_crop_center-center_75/princess-leia-princess-leia-walking-in-new-york-is-just-plain-awesome.jpeg?mtime=20141217123237" width="200" height="200" alt="A photograph of Ali Meredith" class="grayscale grayscale-fade wp-post-image ral-mugshot">
Note the addition of the directory _200x200_crop_center-center_75 in the path - that doesn't exist on the S3 bucket.