If you're saying the transaction is confirmed now, then those coins are now in the possession of the market. You can't reverse the transaction - that is what "confirmed" means. So in order to get your coins back, you will have to ask the market for a refund. Nobody else has the power to make it happen.
The fact that the market cancelled the order is purely internal to them. It didn't prevent the money from being transferred - in fact there is no way they could do that.
It is possible that they will refuse, or that they deleted the private keys corresponding to the destination address before the transaction was confirmed. In that case, too bad. You could try to get your money back through legal process (a lawsuit or similar), but you can't do it unilaterally through purely technical means.
Are you saying that it is confirmed now? Then the market has the money now. They are the only ones who can refund you, so you will have to take it up with them. – Nate Eldredge – 2017-11-18T21:01:04.337
@nate that sounds like it should be an answer, not a comment. – Max Vernon – 2017-11-18T21:15:40.527
1Since late payments happen a lot, most vendors have an arrangement to automatically return them. But sometimes they can't figure out how to return them (because bitcoin transactions don't always have a uniquely-identified sender). Contacting the vendor is best. – David Schwartz – 2017-11-18T22:14:56.807