anonymous users are still able to create new pages
just by typing in
their browser, so
http://mediawikiIP/wikiname/index.php/Garbage
creates a new page called Garbage.
What do you mean by "creates a new page"? It should just say "No page
exists with this title", or words to that effect. That isn't a page,
it's just an error message, that's why it doesn't show up on All
Pages.