Update sql database documentation

First of all, great module. Reviewing the code i got alot of ideas on how to refactor my own modules.
To the issue.
I might be going crazy here but in the api.php file (drupal 7 version)

function hook_privatemsg_sql_autocomplete_alter(&$fragments, $search, $names) {
  global $user;
  // Extend the query that searches for usernames

  // $fragments is explained in the api documentation in detail

  // The query is already set up, it's searching for usernames which start with
  // $search and are not $names (may be empty)
  // the main table is {user} a

  // for example, add a join on a table where the user connections are stored
  // and specify that only users connected with the current user should be
  // loaded.
  $fragments['inner_join'] = 'INNER JOIN {my_table} m ON (m.user1 = u.uid AND m.user2 = %d)';
  $fragments['query_args'][] = $user->uid;
}

Well that sounded fantastic, exactly what i need. So I tried it in my module. Could never get it to work, put a die() in there, and it's not been runned. So I started to look for the drupal_alter(privatemsg_sql_autocomplete) and could not found it anywhere in the source. Am i doing it wrong? Feel free to punch me in the face (prefferably virtually, as i like my face)

Same for the non dev-version btw.