I try to retrieve history of a specified bug in a plugin page.
I use the function history_get_events_array($bug_id) but it give nothing because it call history_get_event_from_row() which use :
$t_project_id = helper_get_current_project();
...

Make sure the entry belongs to current project.

if ( $t_project_id != ALL_PROJECTS && $t_project_id != bug_get_field( $v_bug_id, 'project_id' ) ) {
continue;
}

But in this context the bug is not related to the current projec.