India Post — driving license and verification letter of driving license

Address: Sonipat, Haryana, 131001

My brother has posted me my driving license and verification letter of driving license on 6th september 2017. I am in australia so he posted to australia to my adress. I received an empty envelope on 21st sept 2017 without any content. Australian post is saying they have recieved this as it is from india. Content is missing from india. Envelope was open and looks like someone opened that it does not look like that it was damaged. As per my brother there was one brown color packet was there in white envelope for the safety reason for the contents. But i did not recieved that. Plz investigate where its missing. Driving license is really important for me.