After 3 years I got the solution lol
/ext/javascript/smartsuggest.js
//funcao para esconder div
function esconder(div_value) {
var esc = document.getElementById('smartsuggest');
esc.innerHTML = '';
}
includes/boxes/search.php
add onblur="javascript:esconder(this);" into the input field (call the function when the user clicks outsite the smartsuggest/seach box)
$info_box_contents[] = array('form' => tep_draw_form('quick_find', tep_href_link(FILENAME_ADVANCED_SEARCH_RESULT, '', 'NONSSL', false), 'get', 'id="frmSearch"'),
'align' => 'center',
'text' => tep_draw_input_field('keywords', '', 'id="txtSearch" class="formbusca" onkeyup="searchSuggest(event);" onblur="javascript:esconder(this);" autocomplete="off" size="16" maxlength="30" style="width: ' . '190' . 'px"') . ' <div id="smartsuggest" ></div> ' . tep_hide_session_id() . tep_image_submit('button_quick_find.gif', BOX_HEADING_SEARCH) . '<br><div id="search-text">Use palavras-chave ou os 5 primeiros digitos do código da peça</div><br>');