Actually, Hong Kong postage service is in a quite higher standard and lost mail is seldom.
Of course, this will happen as there are so many points and chances of lossing mails on the way ot processing mail to the way of delivering mail. However, the lossing mail is still in such a low persentage.
I think HK postage in general is reliable and fast.
Of course, if your need to send expensive or very important things, please use registed mail the $13 is in additional that you can sure of the mail delivery status.
My wife went to Canada in April and she send me a post card there but now i don't receive any.I think just depend on your luck.Another case, one of my friend send me a moble also from Canada . I also not get it.