railway rules state the following "No cancellation charge or clerkage shall be levied and full fare shall be refunded to all passengers holding reserved, RAC and waitlisted tickets, if the journey is not undertaken due to late running of the train by more than three hours of the scheduled departure of the train from the station commencing the journey subject to condition that the ticket is surrendered upto the actual departure of the train instead of existing 3/6/12 hours for distance 200 kms/200-500 kms/500 Kms and above after the actual departure of the train"
i.e You have to file TDR ASAP since the actual dep of the train at GMO is 16:20