The problem is at the very start of the boot process, before any module loading.
dmesg doesn't show much 'cause it's as the kernel searches for & initiates any drives it finds, I can't find a log of this part of the boot process, if anyone knows, I'll post it.
The manufactures, ASUS, said they knew of this problem & claimed it was fixed in their latest BIOS update, which was over 6 months ago, so I tried flashing the BIOS but it did not work!! I've even tried the latest one at the time of writing this, but still no fix.
Definitely no rules in fstab or mtab, anywhere else for that matter.
Ain't in the BIOS either, hence a "phantom drive", which is why I want to tell the kernel to ignore it by passing an argument to it via the boot loader.
The kernel line used to be: hdx=noprobe or hdx=none
"Used To"?? Does this still work? 'Spose I'll just try it & see!