This is the hint. The third-party payment provider that is involved in the commercial license, in this case, Paypal, is more likely the one who requested MW to remove OP’s offending models, because they don’t want to get dragged into the process of buying and selling IP infringing products (either physical or digital). Even if OP’s models are not in the program, if the payer happened to see them, they could make a request and MW would comply.
Another possiblility is the car companeis themselves made the request. In that case, probably many more such models had been removed, but OP happened to be the only one complaining.
I doubt MW responds to such reports from ordinary users since they are not the IP owners.