Ive had my clown with bits of sand on it before which worried me into thinking it was ich but if its gone after a day, it may just be sand particles stuck on it.

I think that might be a possibility He is always playing in the sand. His diet is already rich with garlic, but I am still going to treat the tank as if he might just to play it safe

Treat the tank with what exactly? if you have coral or invert in there, there is no medicine that will be effective against ick and not kill your invert or coral.

YOu cannot put copper or cupramine in your main tank as this will not only kill your coral and invert but will also contaminate your liverock with copper.

I would feed well and observe for now since it's the only fish. That might have been just some dirt or sand, hard to say.