Somehow I find that really hard to believe that you were infracted for using just that emoticon- unless that was the only thing you posted. Emoticon/meme replies are seen as spam and if you post just that it may be infracted.
If that was not the case and rest of your post was not breaking any forum rules and you believe some kind of error was made while issuing it - you should contact the staff back for an explanation or review. We try to do our best but on some quite rare occasions, mistakes can happen and a wrong post may be accidentally clicked for it. But it's fixed back if it is brought to out notice.
Send me the Infraction pm you received and I will take a look.