Received application, waiting for your old passport?

Hi I went to the Post Office and did my passport renewal with them. They took care of everything etc, and took my old passport off me to send via Special Delivery/Guaranteed Delivery. That was on Friday 22nd April. I've just typed in my ref number on the passport website and it says they are waiting for my old passport???? Is this just a glitch and my old passport is sat there at the passport office with hundreds of others for renewal and they just haven't updated the info? Or do I need to be asking questions as to why they (allegedly) haven't recieved my old passport??? I never received a tracking number for the special/guaranteed delivery, which I didn't really concern me at the time but now after nearly two weeks I'm getting a little concerned that my old passport has gone missing. Any advice much appreciated.