Can write to datastore, but not retrieve.

[rob30UK]

I made a cron which writes to the datastore, but I cannot retrieve it in any plugins.

Just to be sure Im not going mad I changed my cron code to a very very simple

<?php
build_datastore('glossary_links', 'thisistestdata');
?>

True enough when the cron is fired the data is entered into the datastore which I can see via phpmyadmin.

Now I have tried every which way that I can to retrieve this data and have tried several hook locations but no matter what I do I cannot retrieve the data from out the datastore again. I've tried

global $vbulletin;
$glossary_links = $vbulletin->glossary_links;

Nothing seems to work. Does anyone know the stupidly obvious thing that I am forgetting to do here?