Mercari Mercari.com Allowed the Buyer To Cancel Item While In Transit And Did Not Pay Me Palo Alto California

A Buyer purchased an expensive item from me. I shipped it the next day. The post office lost my item, I informed the buyer that its possible the item may be lost. The buyer canceled the order and Mercari refunded the BUYER, without even notifying me. After some time the item popped up in the USPS database and was delivered to the BUYER. I reached out to the Buyer and asked them to inform Mercari they received the item. Mercari is stating that the BUYER has never informed them. I reached out to Mercari and they are refusing to pay me for the item. I have been trying for Months to get Mercari to give me the money that owe. I even used Mercaris Pre-paid Label. Mercari is stating that I sent the item a little over 2 weeks after the item was canceled. WHAT PERSON IN THE WORLD THAT IS COMPETENT WOULD EVER SEND AN ITEM AFTER IT WAS CANCELLED!!!!!!!!!!!!!!!!!!!!!!