The link actually exists but at present hidden due to hover effect which is occupying the entire width and height of the image. For now, it exists for SEO reasons but will look into ways to have the navigable link without affecting the hover style. Thanks for bringing this to our attention.
Too late for me. My client has asked me to find a solution that works today.
I managed to make the link completely cover the image area via CSS. Success!
Only now, the image title attribute appears. It looks really redundant to have the post title appear in the excerpt below the image, in the image as a hover title, AND as a tooltip.
And I thought WordPress did away with the tooltip for images. Very puzzling.
You can see it in action here:
http://www.susangreene.org/projects/