I have looked at the previous answers for deleting a custom template previously posted, but when I go to the Library, etc. when I get to iWork09 the only options after that are content (which contains only "fills") and Frameworks (which contains lots of items, no templates)
They probaly told you that if you are on a Lion machine you have to in the Finder click on Go while pressing theoption key. Then you get the option of the right Library where you can find your custom template.
This is one reason to not get the lion system.