Some fonts installed on my iMac are missing from InDesign CS6 - how do I find them?

I recently started dealing with a client's brand and they use the BelfastSF font in their titles. Now I come to create some artwork for them and the font that I installed on my iMac is not displaying in InDesign CS6.

Does anyone know why this is happening?

As you can see the font is definitely showing in my Font Book.

Any suggestions would be greatly appreciated.

Thanks, Mike