What to do... US Postal Money order not received.

I've Priority mailed a US Postal Money Order for $610.00 to purchase audio equipment here on AudiogoN. It's been 13 days now and the Money Order has not yet been received ! I've told the seller that he could sell the equipment to someone else so he isn't held up. In the meantime, i'm both stuck without the equipment and embarrased about what has happened. Now, I have to wait 60 days to get my funds, provided the Postal Money Order has not been cashed! What can I do now? What could I do to avoid this from happening in the future? This has never happened to me before. Any suggestions would be appreciated.
Thanks for all the wonderful responses. I'll update the story as soon as the Money Order is delivered, replaced or.....? cordially, Richard
I also just went through a similar experience. I sent a money order by USPS priority mail on 1-18-02. It arrived on 1-30-02. I will not send another letter sized item by USPS priority mail.
The Money Order was received in damaged condition,complete with an appology letter from the US Post Office) 26 days after it was mailed !! I've requested that the Money Order be mailed back to me since the item,with my agreement, was sold to another person. Thanks for all the wonderful responses. richard.....
Use Certified Mail, Registered, Return Receipt Requested - this creates a chain of custody and is virtually foolproof. I have also had good luck with making COD purchases, the equipment arrives and I pay the nice man in the brown uniform...
This is why I COD everything with Postal Money Orders. I get a real scream out of the person who ask that I send the money order first and after they receive it, they will send out the product. Right, I'm going to trust someone with pay first and receive later. I don't think so!

At times, when a person won't COD, I go the "Paypal" way.

Anyway, you've got a different problem. And, the only thing you can do is wait it out.

Sorry! :(