I just wanted to put an ending to this little saga.
I got adventurous and transplanted the EEprom from the 'dead' console to my current working one.
At first I had an issue with a flashing red light, and the console not booting beyond the ind-bios screen (that's what I have on my chip). But, I think it was a bad solder joint as touching each of the 8 legs of the EEprom with the soldering iron seems to have fixed that.
So, as I type this I am backing up all of the irreplaceable data I had on the old drive I had potentially lost, to move it onto the replacement one I have spent time setting up.
Just some settings files and a custom UnleashX skin I've been making on-and-off for a few years.
Other than that, I intend to 'unlock' this drive and put it into another project.
I know I could leave it in the console, as well as the EEprom chip. But, I intend to put the original EEprom back once I've finished my back-up and 'unlock'.
Thank you for the offering of information and helpful suggestions and guides.
If I only learn one thing from this experience it will be to leave well-enough alone and not bother locking XBox HDDs in the future.
Like I said; I'm just putting a more happy ending to this particular story.