I recently bought a WD My Cloud NAS and attached a WD USB Drive to it. After pulling it out, it seem to have corrupted the USB drive and on running first aid gives the error as shown. I have tried using Tech Tool Pro but it fails with validation error on selecting the greyed out drive. Would Disk Warrior work (?), I would have to buy it though! Any ideas please on how to fix or have I lost my data? I am on Sierra. Thanks.