I have thought about it, and it seems the shrimp has culled itself since I got home. I suppose the stress was too much for the poor thing. I was trying to use her as an experiment to see if there was a quick fix for this disease, whatever it is, in case it popped up in the community tank, as it might have been carried on the other Rilis. It looks like there might not be, but luckily I haven't seen it on the other shrimp... though I have had two deaths since I added the Fire Reds--not sure if they were the previous shrimp or the new ones. It's seemed to be one yesterday and one today. The others are very active and scooting around the tank as normal.
I hope they are just random deaths and not related to whatever got the Rili.
Thanks everyone for your advice!