Why do I get "Theme hook ... not found" after renaming?
function questionList_theme(...)


must have the name of the module, like :

function survey_theme($existing, $type, $theme, $path)
{
    $variables = array(
        'questionList' =&gt; array(
            'variables' =&gt; array(
                'questions'    =&gt; NULL,
            ),
        ),
    );
    return $variables;
}


will work.