FBM – first return, please help!

We sell large furniture items and ship from Canada to the USA. We sell on Amazon.com (US). We had our first return because the buyer “didn’t have storage” for her large order. Since we are international, we provided a prepaid label for the buyer to use to ship back the items and provided clear instructions on how to ship the items back. I even booked a courier pickup for the buyer because the items are so large to take to a post office. It’s been 2 weeks and the buyer has not given their item to the courier. Is there anything else I am supposed to do as a seller? Do I not refund them until I receive the items back? What if the buyer never gives the items to UPS – is the return void?