Short answer is, "It depends on why the item was returned, but probably not a great deal."
An item returned after reaching the destination country is usually returned because either the buyer refused the shipment, was unable to collect the item from the Canadian carrier's hub, or else the carrier somehow bobbled the shipment.
All of these scenarios would be covered in the "Undeliverable items" section of the eBay International Shipping (eIS) terms and agreements for buyers purchasing items where the service is used. There are links to these terms on the listing page, and as with the old Global Shipping Program (GSP), buyers agree to those terms by purchasing an item where the service is used.
The most likely outcome for a return from Canada would be that the item gets returned to the forwarding hub or a location nearby and is sold off to a liquidator. The seller would keep the funds from the sale and if the buyer isn't automatically refunded, they'd have to try to pursue a refund themselves. In the case of a refused or uncollected shipment, the buyer might not have recourse for a refund through eBay and would have to see if the payment method they use has provisions for contesting charges for undelivered internet orders.
I don't believe there's a telephone number that one can use to determine the whereabouts of an item forwarded through eIS. Some people seem to have had luck contacting eBay customer service through Facebook or X / Twitter (not by phone), while others have found that using a third party tracking service such as Parcelsapp provides event scans and information that isn't viewable on the eBay site.
Hope that covers your questions. Good luck!
