There is a wizard here that will walk you through the steps -

http://www.yvr.ca/en/navigating-yvr/...rough-yvr.aspx

At that hour the 'quasi sterile' transit is closed, so you'll need to enter Canada.

...however, as you need to pick up some stored baggage this would have been your only option either way. So you'll proceed to the Canada Border Services Agency check point, enter Canada, claim your bag at baggage storage, then head to International departures.

Be sure you check the baggage storage hours.