check your outbox and see if theres the message that you sent. If theres nothing there it means they;'ve read it and too lazy to reply to them pm straight away
What I mean, is that when I click send on any PMs, it redirects me to the FTO Australia home page, not the 'PM sent' page I'm used to seeing after clicking send. The PM then does not appear in my 'Sent Items' or 'Outbox'.