Answers: The shock of one dropped (including possible physical injury) as well as being introduced to a new environment could okay mean that you fish is beyond help. New fish won't generally devour for several days when they're healthy anyway - all you can do is maintain the water quality immaculate and hope the fish recover.
Do you have this fish alone or in a shoal? They need to be within groups of 6 or more.
More then likely this is actually nought you did. It sounds more like he could not take the stress of the move. If it continues to struggle them I think i would in actuality return him to the store and get a health one. As other things could be wrong as well influential to a pollution of your whole tank and a loss of all your fish whether not careful.