Yeah it's completely under the radar.
I bought a 'HPI clear' Corrado VR6 back in 2003. Shortly after purchase, I wondered why paint match rattle cans were way off, but I put it down to the paint shop's blend being off. Roll on a couple of years. As I was parking up at B&Q, some random bloke approached me and told me the car used to be his Son's, which he duly wrote off. I couldn't work out what this chap had to gain by telling me that, but thought to myself "Bullsheet, it's HPI clear, what a weirdo".
I never could confirm the truth of it, but it later transpired the reason the rattle cans weren't matching was because the car was repainted down one side at some point, so I think the man was telling the truth. Further confirmed by the same paint code ordered from 4 different mixers. None of them matched the car, but all matched each other. Smoking gun right there. I was fuming. I hate being duped, but it just goes to show you can't rely on 'the system' at all. Always trust your instincts.
The body shop did a very good job to be fair, which would have cost the fool £1000s of his own money. This guy must have had a very good reason for doing it off the books. Drunk driving probably. Better to lose a few grand than your license if your job depends on it.
And if that wasn't bad enough, I bought a mint low mileage MK4 R32 about 6 years ago, also HPI clear, and that turned out to be dodgy as well.
So be vigilant peeps. I'm done with s/hand cars as people prove to be untrustworthy time and time again. My next one will be brand new, or newly new from a main dealer.