If you want the ajax search module to search through ID of properties, please follow these steps:
open file
components > com_osproperty > classes > listing.php
find
if($search_name == 1){
$query1[] = " a.pro_name like '%$keyword%'";
$query1[] = " a.ref like '%$keyword%'";
}
change it to
if($search_name == 1){
$query1[] = " a.id = '$keyword'";
$query1[] = " a.pro_name like '%$keyword%'";
$query1[] = " a.ref like '%$keyword%'";
}