How to diagnose why plugins don't show in Photoshop?
One thing to try is to find the Photoshop application, and Get Info on it. You can do this by selecting it in your Applications solder and pressing Command I or right clicking and choose Get Info. If you see a check box marked Open in 32 bit mode try selecting it, and then launch photoshop again.

Plugins for all programs generally need to be 32 bit if the host app is running in this mode, or 64 bit if the app is. 

This is from experience with Logic plugins, which would refuse to acknowledge some older 32bit plugins when running in 64 bit mode.

Having typed this, I've since found this relevant page: http://kb2.adobe.com/cps/828/cpsid_82824.html#main_32%2064%20bit%20launch