Currently, the #lst parser function does not display anything when the section name given to it does not exist. For example {{#lst:My_page|foo}} won't return anything if the "foo" section of the page "My page" does not exist.
It might be nice in this case to auto-categorize the page in a category named something like "Category:Page attempting to transclude not exising section" to allow contributors to check and fix these issues.
First reported on French Wikisource.