Air India — missing luggage

Address:

Jalukbari, Guwahati, Kamrup Metropolitan, Assam, 781014

I traveled from madrid to gauhati via frankfurt and delhi. I had to collect my checked-in baggage in delhi for customs clearance and was asked by air india personal to check-in in delhi in flight no. Ai891 bound to guwahati on 27th august, 2019. One of my checked-in baggage bearing bag tag no. Lh663461 is missing. I had checked-in at around 10:30 hrs for a flight with departure time of 16:10 hrs, and air india's representative says that my luggage was received lately. I have registered a complaint at the air india ground staff at gauhati with file reference no. "gauai12062". I have been checking in online worldtracer in air india site, and it still says "tracing continues. Check back later". I have tried to contact the air india personals at gauhati airport several times via phone, and they say they don't have any knowledge of the whereabouts of the missing bag, and will inform me later. I have very important documents and materials in the missing bag. I am desperately waiting for the missing bag.
Sincere regards
Pranjit