For starters, it should be noted that removing a domain name from your account doesn’t change any file or database entry. If all you did was remove the domain from your account, all your files are still there. But note that adding the domain name again does not always assign it to the same directory. In that case, you’ll need to move your files from the old website folder to the new one.
If you did actually delete the files, then the files are gone. We don’t provide any kind of backups or snapshots with our hosting. So any change you make to your site is permanent unless you have backups yourself.