What do I do if I entered the wrong tracking number on a return?

[cyberenddragon92]

I believe I may have entered the wrong tracking number on a return, and I cannot for the life of me find a way to view the return shipping label that I printed out and attached to the box again. Is there a way to view that shipping label again? I shipped it quite a long time ago, and the status of the return says that it has not moved at all, and when I plug the number I entered into USPS, it shows that the tracking number does not exist. With this mistake, can the seller now say that they never received the item back and keep my money AND the item?