Will Canadian Immigration Know What Coutries I've Been To?

Basically, I have been granted a working holiday visa but on my application I only stated that there were two countries that I have resided in for over 6 months when it is actually three. I have Police Certificates from my home country and the country from which I was living in when making the application, but there is another country I have lived in from which I do not have a police certificate.

I have a new passport since living in this country so there is no physical indication that I have been there, but will anything flag up when I actually enter Canada to start my visa?

Thanks.