I would suggesting finding a new LFS
if the one where you frequent is selling Morish Idols. These fish were given a 97% captive death rate by a group of scientists, and after reading about the numerous failures with keeping them I would like 98% or higher is likely.
At any rate like Fluff said getting an idol to eat is just one step to suceess. Something they consume in nature cannot be replicated artificially and most of these fish die from lack of nutrients over what is sometimes weeks - months to years. They only strive in overly established tanks where natural food sources are prevolent.
I would contact the LFS
where you got him about a possible return and if they will not cooperate and take him as a return I would report thier nature to the Better Business Bureau and MAC.