You have four tools.
The first is using a “tracked” service to return the item. For most items only Delivery Confirmation is required. These services include Expedited, Tracked Packet and (in Canada ) Regular Parcel.
If the value of the item, including postage, is over $250 you must also purchase Signature Confirmation.
The second tool is appropriate feedback. You have 60 days to leave feedback.
The third tool is Detailed Seller Ratings. These are left at the same time as feedback but are much more important to the seller. A normal transaction gets a Five Star rating. The lowest Rating is ONE Star. No Stars is a Free Pass.
And if worse comes to worst, you can Dispute the transaction through eBay as Item Not As Described. You have 45 days for this and must prove the seller has received the item back.