There are actually two ways to do this: as posted on this site you can add the following just before the close of body tag:

<script type="text/javascript">
$(function() {
var grid = jQuery("#TABLE_NAME");
grid[0].toggleToolbar();
});
</script>

OR

comment out the following line in cls_datagrid.php. I like this method because I want to show this more times than I don't, so it is easier. Basically you are deciding the default behavior of the integrated search: leaving this un-commented makes it hidden by default which requires you to use script to toggle it on OR you can comment it out so it shows by default and then will require the same script to hid it.

//echo 'phpGrid'. $this->sqltable .'[0].toggleToolbar();'."\n"; // hide inline search by default