If your parameters are good hang in there.
In a barebottom 75, I have a long spine urchin. Not thinking, I poured some fresh water in really fast (instead of carefully) and it totally stirred up the detritus on the bottom of the tank.
Other than making a cloudy mess, I didn't think there would be any lasting effects. Well, the next day there were spines all over the tank. The urchin was hiding behind the rocks and wouldn't move. I felt really bad and after a couple of days of not moving, thought he was a goner.
I took a small rock, attached a bunch of nori with a rubber band, and put it right next to the urchin. It barely touched it. For a few more days, I would continue to try to feed it and it would barely move from its spot.
After several more days, it started moving around the tank and I could see the spines growing bigger and bigger each day.
Months later, it's totally back to normal.
Lesson learned.
I also have a tuxedo urchin in another tank. Given my experience with the long spine, I'd like to think yours could recover to.
I think with most critters, if it eats, it's got a chance to recover.
Best of luck,
Roy