I have a document where the footer has disappeared.
I don't mean that the content has disappeared; if you do View | Header and Footer and then click the button to go to the footer, it doesn't display anything and the insertion point is still in the header.
If I add additional footers (e.g. by going into page layout and setting a different footer for the first page) then the first page footer appears, but not the one for the other pages (the "Primary Footer").