Funny you should mention, sheep. I'm in exactly the same position as you. In all my time on eBay (10 years) I too have never once had a posted item go missing in transit. Not ever, and even though I clearly put my name and address on the backs of everything I send, I've never even had one returned as being undeliverable.

Using AP's own figures, it would seem that they lose or misplace (or have stolen) around 1 item for every 1000 posted (or 0.1%) and if you've ever been to an Australia Post uncollected mail auction, you only have to look at the way most of those items have been misaddressed or packed to understand why they were undeliverable and unreturnable to their senders.