j-1 no objection letter's case

china embassy already sent my objection letter to dos. but i just read the instrution sheet from dos. it says i need to ask the embassy put my case number on the top of the envelop of no objection letter when the embassy sent it. i didn't remind the embassy before. can anyone tell me if the embassy will put case number on it? anyone has the same j-1 experience, please help me.