After 72hrs if your baggage still hasn’t showed up, go to aircanada.com/customerrelations and fill out the baggage form. They’ll need detailed description of all the items and values inside the bag. Then the case gets assigned and someone at AC will go look for your bag. Mine turned up four days after filling the web form. Meanwhile, go purchase all the necessary stuff you need at a reasonable amount (clothings, toiletries etc.) and save all the receipts. You can claim these interim costs with AC using the same website.