With this macguffin's loss, the thread of prophecy is severed. (Spoilers!)
YouTuber BOB_BestOfBugs, however, realized that there's nothing stopping you from putting a Netherstone into a container like a crate or a sack (crucial to the Shadowboxing speedrun tech) and then getting rid of that container. I was able to replicate the trick in my own game, but curiously I only got the game over on losing my second Netherstone, so watch out for potentially soft locking yourself here.
What follows is the most luxurious sort of "you messed up, big time" scene you could possibly ask for, shades of firing a mining laser that wipes out all of humanity in System Shock and its remake.
Also I saw that cutscenes once before making it as far as you describe, I don't even remember how, pretty sure it was midway through act 2. But it's definitely a semi generic cutscene for when you lose in a particular type of way.