An Entire Folder is Missing From My External HDD

Hello,

This morning when I booted up my PC and connected an external HDD to it, I noticed an entire folder missing. I know its still there because the drive's properties say 11.8 GB free of 146 GB, but when I selected all the folders in the drive and checked out their properties, it only amounted to 55.1 GB.

I have tried everything given on this thread -> https://ccm.net/forum/affich-623304-hidden-files-on-my-hard-disk to no avail. I scanned the drive with Bit Defender however it returned nothing.

Tried Autorun Exterminator and Malwarebytes Antimalware. No joy.

When I try out the CMD attrib command, I get several access denied messages though...



My PC has Windows 10, and Bit Defender. I have tried running the HDD on a laptop with Windows 7, but can't see the folder on it either.

Will really appreciate any insights into how to resolve this issue.

Thank you!