Examples without pages

I sometimes see examples that don't have a page on a Trope page. For example:

• In Random Work, Bob sits on a chair.

Are these allowed? Can the works be left alone and have no page? Or is it recommended to make a page for it?

You can write example entries for works that don't have pages (as well as redlink them). You don't have to create the page in order to add examples to tropes pages.