Just searched for '1955211' in the SO search field.
Expected output: include the question/answer with ID '1955211' in the search results. If the search result set is a single question/answer, redirect to that (I seem to remember, that is already the case).
Actual output: the 'no results' page showed up.
How to fix: If the search term is /^[0-9]+$/ (or whatever a valid question/answer ID is), look up the ID database and include results with the queried ID.
Complicacies: May provide results that are not (at first sight) correlated to the search query, e.g., when searching for 127001 or 123456.
Problems steming from complicacies: If someone can't distinguish between the different result types, he should perhaps re-consider giving answers on SO.