Regardless of if it's frowned upon to model cars, they were in the public eye. Therefore the chances of them getting collared were increased ten fold. The world of a car model is probably a vacuumous one, chances are they were too occupied with their hair, make up and which tit to flop out to think about the fact they weren't entitled to work.
It's in your own interest to make sure you're hear legitimately. If you're not and annoying pedestrians on the shopping street with leaflets, promoting at Mr Wong's Jade shop or anything like that, all in the public eye then it's likely you'll come unstuck if you're not qualified to work.
If you find yourself teaching out of Mrs Miggins' kitchen on a weekend, or working for some experimental training centre, or you teach 1000 hours a week for a pittance, it doesn't take brains to presume that something's a miss. You can't act the victim when you're caught.
You can spot these kind of places from the off.
'Come to our Christmas party/ English corner, just to meet the students' - Work for nothing we want to market people we could never pay.
'Can you do an unpaid demo class for us' - We just need someone to show up and work for free.
'Pay depends on the amount of students' - We have no idea what we are doing, but we've heard its lucrative and need a gullible foreign idiot.
'We offer a competitive salary' - We'll just hire whoever is the cheapest, we don't want to commit to a price if someone is willing to work for less, that's the kind of guys we are.
'We can HELP you get a work visa' - We can't hire foreigners.
and any advert were they begin quoting the price of a bowl of rice or a carrot in a local market to justify their awful pay.
No teacher worth his salt would engage in that sort of nonsense and any school with even a passing interest in professionalism is going to hire you on the basis of your CV/ qualifications and references, like any other job would.
Any Chinese dolly bird could model a car, a migrant worker could hand out leaflets, a local with knowledge of Jade may be more beneficial to Mr Wong's shop. These are not the expertise that China is lacking, so you'll find your case won't be looked on favourably by the powers that be.