Might be different in Vic but in NSW (a few years ago now) my mate had his rego cancelled because he did what Alex said, failed 1st inspection at joe bloggs, went elsewhere failed again, went back to the 1st place and passed, 5-6 months later he got a letter saying his rego was cancelled due to a failed inspection at the 2nd place, because different things were wrong/listed with the car compared to the 1st inspection (joe bloggs), So he had to get the car re-inspected.
hope that makes sense...there are losts of 1st place 2nd place in there.
Whether he was just unlucky and someone clued on at the RTA office stumbled across it or they actually go looking for it I don't know, but it can happen.