Indigo Airlines — Baggage missing for 8 days! No communication!

Landed in Delhi from the UK via Istanbul on 7th December
Airline staff at Istanbul suggested putting hand luggage in the hold as flight was full and that the 2 pieces of luggage would be on the belt at Delhi airport on arrival
Reached Delhi and only 1 bag arrived
The missing bag was the bag with OCI visa and some ££
Filed a report and after 10 hours at Immigration - being questioned like a criminal was granted a temporary visa for 72 hours
Applied for a extension visa immediately and now waiting for an exit visa which is taking time and I need to leave in 2 days!
IndiGo are taking absolutely no responsibility, have not even communicated and it has been 8 days!!!
Appauling customer service and airline never known anything like it.
I am hoping there is someone that is going to be able to help as I have 24 hours to find my bag with my OCI!!!