Since Canada Post says the bag was picked up, you should file a Not As Described complaint with eBay, and supply the number of the return shipment.
EBay will refund your money and then go after the seller for it. There will be other penalties.
BUT
If the original payment was over $250, and you did not use both Confirmation of Delivery and Signature Confirmation, you will not be refunded.
Only DC is needed if the original payment is less than $250.
You have only 45 days for this complaint so act now.