Hi,
Thanks for your response.
The error message you quoted was indeed the very first message I got after the physical hard disk that stored the virtual disk was accidentally unplugged whilst VMWare Workstation was in the process of deleting one of the disk's old saved states from the Snapshot Manager. That's how I ended up in this mess.
However, I no longer get that error message, and instead, now get the error message that I originally posted regarding it can't find one of the snapshot disks it depends on,
Sadly, running -vdiskmanager -R command results in no errors being found against that .vmdk or any of the other .vmdk's associated with that virtual machine.