Hi Vishal,
This does look like it is an Airtel number. And "The no. doesnt exist" usually will come for a number reserved for an outgoing only connection viz what telemarketers use. As it appears to me, it is a telemarketing call. As regards to it being a blank call, it could be a hundred reasons...connection issues, network problems etc....So relax and let it be and ask your father to do the same too.
P.