This is the most easiest way of reading a Text Message in Friend’s Phone. But he will not know about it.
Open Inbox, without opening unread Text, click Options Menu and then select Forward or Edit. And in Editting Mode, you can read the Text but it would remain unread.
Open Inbox > Unread Text > Options > Forward or Edit.
This trick works with the all Nokia Series40 Phones. Symbian trick will be updated soon.