If the guy did have ich, moving it for a few days to be extra sure is not a bad idea.
Also, That's why I asked for Pictures. I know my Six Line Wrasse had what looked like to be ICH, but it was simply sand stuck on him because of the mucous membrane they create when they go to sleep.
I am glad they don't get ICH, so if that's the case I believe QT for a few days will not hurt it, and it should be put back into the main tank as soon as possible. I wouldn't risk my Main Tank, if I did not know Mandarins couldn't get ich!
Fish Sticks, the best thing you can do with your dead fish.