Devils hand,common names are so tough.Could be Lobophytum sp,maybe a Sarcophyton sp,either way its most likely a leather coral.It is normal for Leathers to go into periods of recession/dormancy.They shrivel up,look sickly,no polyp extension,etc..This can last from days to weeks and can occur once a month or hardly ever.Either way,its a normal behavior.The coral will re-emerge shedding a waxy coating(tunic) and will be healthier as ever.This sheeding is highly toxic to some corals and if possible,remove it from your tank.