Footer style not in Available Styles list

I posted the same problem in mac.office.word, but perhaps gave too much
detail.

I'm creating a document to turn into a template for chapter books. In turn,
that template will be the starting point for a short book template and a
third template. That means I want to make sure this document and thus
template is rock solid.

After some difficulty, the document seems completely fine except for the
Footer style. The style is still applied to every footer, but the style
itself doesn't appear in the Formatting Palette Style List Available
Styles, although every other style used in the document seems too.

The Footer style does, however, appear in the Format Style Styles in Use
list. It also appears in the Formatting Palette if you switch the list to
show All Styles.

Why does the list no longer show the Footer style under Available Styles
like it did before the problems? Especially since it's a built-in style
that's being used in the document.

Although there's the obvious work around, I'm nervous about creating
templates and documents off this without resolving this issue, or at least
finding out what caused it.

I haven't found anything in my searches on where the Available Styles is
populating from.

Thanks for your time.