Take my money and do not offer something in Return

I made travel reservations on BA operated by Comair from Jnb to PLZ and Return on the 7th from Cpt to Jnb. I fell ill and was hospitalized prior to my departure in the inward flight. When I tried to check my luggage to utilize the return flight I was told that I have no longer a valid ticket. Very rude counter personnel insisted that I simply buy a new ticket or disappear from sight despite providing all proof that I was ill and therefore unable to use incoming flight. Surely it cannot be fair if you have paid for a service it being refused simply because you were ill and could not use the initial part of the service!!!