Psssst, yes, they could drive past a thousand Patrols wondering which ones have Airlockers, HID's, Chips, etc etc ... or... they could come on to enthusiasts sites and find a whole bunch in half an hour.
No biggee to me whether people block out plates or not... just saying I have first hand knowledge of two instances where exactly that has happened. Surf the net, get the plate, get the addy's, get the gear. Gaol time for one instance, insufficient proof in another.
It's called risk assessment people... totally your choice and agree the odds are low but it most assuredly does happen only the prevalence is debatable.
As for the Coppers surfing the web looking for defects, well, I dunno about that one. In the case of the Jeep Forum maybe thats how it went down, maybe not but even that is different to Coppers proactively looking for specific vehicles to defect.