Please note that everything that you see on screen is not searchable. The search that you are performing is using SharePoint search engine behind the scene.
SharePoint crawls the fields that are meant to be searchable and those that are marked as "Indexed = true". ID field is not indexed so you cannot perform ID based search.
UPDATE: If your library is more than 5000 items, you might as well be victim of stupid in-place search. Check my blog for interesting findings: http://the-sharepoint.blogspot.com/2015/12/strangeunexpectedfrustrating-in-place.html