On your default page, left hand column at the very bottom is a 'Pages' Section. Click 'like pages'. At the top of the next page, you'll have 3 tabs, on 'Invitations', you should have a number in red, click this and you'll see all the pages that you have been invited to like. The official Project Puma page should be one of them.
Although I don't understand why you can't see the page, as it's not a private page, so anyone should be able to see it.