I get to use my plant biology degree today!

So coconut husk is made up almost exclusively of lignin. Almost nothing on the planet can digest lignin (termites, beavers, a few detritivores, and some bacteria are about it). It won't look any different going out than going in. Cocofiber isn't safe because it's digestible, but because the particles are so small that they can pass through the system without blocking it up, and it doesn't swell up in the digestive tract. You just can't really see it in poop because it's small and brown.

Yeah, even if you had pulled it, I think the damage would be really minimal. I personally see no way that wouldn't be resolved with the next poop, but if it somehow isn't, that might be the time to gently try and pull it out.

(Also just make extra sure it's coming out of his vent and not just wedged between the scales).