I have been having quite a few problems with trading recently (odd since I haven't had a problem with deckbox for almost an entire year) and need some advice on a current issue. I made a trade with someone at the end of September for some mantis riders and a land, and very soon after mantis rider spikes like crazy. He mentions the price spike but says he sent his half, and I had already sent my half as well. Fast forward to Mid october- neither of us got tracking and neither of us have received our cards. I have the feeling in the back of my mind that he changed his mind and never sent after he realized the price of mantis rider went up, but this is just the cynic in me and I have no way of knowing the truth. Anyways, I cancel the trade because nothing could be done to prove either side and took my loss.

Here is the current issue: A week later he messages me saying "Fyi I got my cards back yesterday thrashed anything on your end?"
I had not received anything so I felt no need to reply. Another week goes by and I get another message from him. "Yours arrived I shipped them back you should have them"

So apparently he got my cards almost a month after I sent them, after his cards were sent and "returned thrashed," and he sent them back to me. Now since it has been almost 2 weeks since then and I still have not received my cards back, how do I go about opening a BTR on an "ended trade?"

It should be the same as any other BTR.