I slid further face down on the asphalt than the board ghost rode after me.
That's because the instant your foot came off the front pad, the OW DID lock up (brake the wheel), because the board stops when you come off it. That's what it does to prevent it from rolling away downhill. That's its version of a "deadman switch".
I'm sorry, I know what you think you felt, but there's a YouTube video out there where a guy does some quick napkin calcs on how quickly the nose can drop down from level to pavement, and it is tiny - TINY - fractions of a second. A nosedive happens FAST. Faster than a human can easily perceive it if you're the one doing it, especially if afterwards you are hurtin' for certain.
You're going through exactly what I went through (boy oh boy do I identify with the "lulled into a false sense of being within known performance" bit.) I share your hope that FM will continue to improve these machines, because they are amazing. They feel like magic and that fools us into thinking they are. But they are still just complicated levers, subject to physics.
Think of two people arm-wrestling (you're one person, the board is the other) - you might strain against one another for seconds, even minutes, appearing to be evenly matched, but when the breaking point comes, when one side can't hold the other's "push" and leverage back any more, the end happens quickly and it's over.
You outweigh the board, by a lot. You "beat" it, by "attacking" it quickly and overwhelming its reserves of strength.
Unfortunately, the nature of THIS contest means that the pavement will always win in the end. Overacceleration can be thought of as fighting the board. Work with the board instead. It WANTS to keep you upright.
Definitely get the Fangs (I did). Like you, I suspect they would have bought me a little time to AT LEAST bail better, if not recover entirely. (My friend who has them on his board has actually ridden out three nosedives on them, staying onboard and bringing the nose back up to continue riding).
Again, I know this isn't what you want to hear, because it's not what I wanted to hear. But since I've learned to watch my acceleration (and this is harder than it seems to always remember - sometimes when you look down an intersection and see a car coming, the urge to scoot across quickly to beat it is very, very tempting. Don't give in to that temptation, unless you want to be lying in the street in front of that car), it - knock wood - has never happened again.
I've read so many post here and on other forums from riders asking for a software or another fix to reduce nosedives. I have almost no experience with only 19 total miles, but as a retired mechanical designer, I don't understand why they haven't added 'fang like' wheels built into the board themselves. I read someone claim they can't do it because it's an admission they made a mistake and it'll open them up to lawsuits.
I don't understand why this would be different than making any other product safer. I can't imagine car companies were sued for adding seatbelts or other Improvements. What am I missing?