Pass two options with the same value into the JLayoutHelper render for joomla.searchtools.default, such as in:
$args = array('view' => $this, 'options' => array('filterButton' => 0, 'filtersHidden' =>0));
echo JLayoutHelper::render('joomla.searchtools.default',
$args,
null,
array('debug' => false));

Expect the filters not to be hidden and the 'Search Tools' button not to show but the 'Search Tools' button is still showing.

Running Joomla 3.3.3

Traced issue to file layouts\joomla\searchtools\default.php line 25. Both array_merge and array_unique are being called on the 'options' array. Remove the array_unique call; it is making it so that if two options with the same values are used one of the values will be deleted.