You need to have grabbed the prefixid in your query for the threads. Then in the php (your plugin or page code):
PHP Code:
if ($latestthread['prefixid'])
{
$latestthread['prefix_plain_html'] = htmlspecialchars_uni($vbphrase["prefix_$latestthread[prefixid]_title_plain"]);
$latestthread['prefix_rich'] = $vbphrase["prefix_$latestthread[prefixid]_title_rich"];
}
else
{
$latestthread['prefix_plain_html'] = '';
$latestthread['prefix_rich'] = '';
}
And you can use one of those in your template.