Recover FIles/Folder from sudo rm -rf Terminal Command
The command you ran first deletes all files and folders in /PATH/TO/COPY; note the warning above the command in the article you linked to: "Next, remove the existing Downloads folder (make sure it is empty first)."

Though the data is probably still present on the drive, the operating system now has no idea where it is.

Assuming that you don't have backups available, your only option at this point is probably to use some kind of file recovery software. This answer at Superuser has some links to potential options. PhotoRec is a free, open-source solution that might work.

Best of luck, and be sure to back up your data (ideally to multiple places) in the future.