Leaving aside statistically what happens, I can tell you anecdotally that products that were destined for Canada and were sent back have found their way back into Canada. That happens.
Statistically, I can't tell you how often, but counterfeiters are quite aggressive, and they will find a way to get it back in. Yes, sometimes they will bring it to another country, but if they want to get it here because they have a customer here who wants it, they will get it back in through another port.