Pinterest button not showing up

On my site, I have a “Featured Photo” category, entries within which feature — you guessed it — a photo. A large photo. An example can be found HERE.

Problem: The Pinterest button never shows up on pages within this category. It shows up on pages for all other categories. Anyone know why? And, more importantly, how to fix it?

Thanks in advance for any help you can offer.

http://wordpress.org/extend/plugins/really-simple-facebook-twitter-share-buttons/