Oh, I understand fully. I just know what the PO can do to mail first hand AND through my work, sadly. I've had to send back payments at work because the checks/money orders have been completely obliterated by the post. It's actually rather sad sometimes. ^^;
I've had a few of my etsy sales never show at their destination, and I was 99% the buyers were being upfront with me. For me, it's often postal errors than scammers, it seems. I once bought a LP on Ebay, which never showed after waiting almost 3 weeks (and he had sworn that he had shipped it asap,) so I got a refund through paypal. It showed up a month and a half later, with a postmark that showed that he HAD shipped it when he said he had. I sent him his money again. Wacky stuff~