Buyer complaint but won't return item

[freereign]

I had someone buy a slightly rare music CD from me. When he received the item, he complained about the condition of it. I told him to do an official return, and he initiated this return. I was given a tracking number but the tracking number shows no activity after nearly a week. I also notice this person sells items like mine for higher prices, so if this CD had a scratch, he could easily have it polished and sell it as "like new", so I am suspicious that he is not returning the item because he will re-sell it after "cleaning it up". The thing is, seeing a person is a Seller, I don't care if they buy from me and re-sell. We're all in this together, so in good faith I issued a refund, thinking the Postal Service had not updated their tracking.  While I don't want to interrupt another Seller's business with a complaint or a negative review, I don't know how to encourage him to complete the return, in good faith.