Let's say you have this template code which sorts some children for a given node:

<br/>search sorted by product name:<br/>
{def $srch=fetch('ezfind', 'search', hash(
           'query', '',
           'limit', 20,
           'subtree_array', array($node.node_id),
           'class_id', 'article',
           'sort_by', hash('article/title', 'asc')
           ))}

{foreach $srch.SearchResult as $s}
   {$s.name}<br />
{/foreach}

Now, create a folder /News and populate it with a few objects
You'll notice that articles are sorted like a charm
Now, create a new article below top node
Then move that article to /News.
That article will not listed before you republish it

ps:
Tested with ezfind, but pb thinks the cause of the problem might be that moving an object to an other node does not trigger a search engine update. Therefore I report it here in the ezp tracker