Are you saying people employed to manage these numbers on the governments behalf aren't sufficiently trained to find numbers in the factory locations Greg? Surely not.
When I originally bought my Sandman and got the rego switched from ACT to NSW the engine number showed up as stolen 20 years before. Dad spent a whole day hanging round the cop shop while they investigated and cleared it with the insurance company. Then when I went to transfer from Dad's name to mine a few years later I got the same thing. Took it to the cop shop, left it with them and when I came back they said "There's no engine number on that block. Here's a Police number you need to go and get stamped on it." It wasn't the original block for the car so didn't bother me. Turned out they'd been looking at the blank spot on the wrong side of the block. The old engine number was just under a bit of grease.