Thank you both.
It was shipped via FedEx to me, the seller definitely did not declare the value because I did not pay any customs (and it was FedEx and not USPS, so I would have been asked to pay customs if it was declared). I will have to check the box at home to see if there was a commercial invoice or customs declaration. There was no return label.
I emailed the seller yesterday asking if I could purchase my own return label and send it to them, because I don't mind paying a couple hundred for shipping, but I don't want to lose thousands by not returning it on time. However, I did not get a response back.
I just called Ebay concierge and they told me that I can purchase my own label with signature confirmation, upload the tracking to Ebay (and that I would be reimbursed for the shipping cost eventually, but whether this actually happens is not a big concern for me, since I was prepared to pay my own shipping). I will go through FedEx, because they are usually the most helpful with paperwork assistance.
Does this sound like an appropriate plan? I know that ebay CS sometimes gives out misinformation.
Also, I should marking it as "Returned goods" on the customs forms and write "Return to seller" on the box? THANK YOU FOR THIS TIP
@xiangxiang0731 ! Do you think I would still declare a value, or does the "returned goods" designation take the place of a value declaration?