At least it was an unrestricted street and you subsequently didn't receive an expensive parking ticket :)
Unfortunately, right here in my city, I've seen TV reports of similar type things happening with people in seemingly-legit-looking vests, shirts, hats, or fake badges, whatever ACTING like an official at flat, open parking lots and collecting money, showing where to park, and later the payer realizing they had been scammed when they found one of those violator boot things on their car...........BECAUSE the lot was the type where they were supposed to deposit money into slot box or pay at some sort of machine and put a chit in their windshield......but then later, the real parking lot monitor came by to boot or issue citations to those who had paid the proper pay. There have even been photos of the people (the scammers) on TV from time to time. No wonder Uber seems to be so popular for going downtown among those who enjoy concerts!
But, that scam would be an easy one to fall for, as sometimes such legit people (employees of the parking management company for open) are on site during popular event times......how would one know what's legit and what's not for badges/attire, etc." And, would one DARE park there where the scam artist is "owing" the lot after pointing out his scam?....no telling what he'd do to your car while you are in the concert....THAT could be much more expensive!
You are right - we need be beware even here in our own country!!