It happens.  The forgotten sash.  Don’t go home and skip class!  Although it’s important to remember your sash, it’s more important to attend class and develop your skills.  Simply follow this protocol.  You are to go to the back of the line and stay at the back of the line for the duration of the class.  If the instructor calls out your rank, then you go up and do as instructed, but you are to remain at the back of the line.