Which airline issued the tickets? Have you asked them if the ticket has any residual value? The fact that you have not received notification does not mean there is no remaining value.
It was Lufthansa. At the time of cancellation I was verbally told on the phone that I cannot get anything back from the tickets cost as it was being cancelled the day off the fight. However I do not have anything in writing from them. Trying to get in touch with them about 4 month old reservation will be nightmare but I may have to try?