I stole a free chocolate cake from a special needs kid

My friend runs a weekly quiz night in a small British town, and I often help him out with clearing the plates away and making sure everyone is happy. It is a town that is slightly suffering, with many young people moving away to find work and leaving behind a high street full of charity shops, cafes and curtain shops as well as the usual pubs and estate agents. I was clearing the plates from a table of three adults, and noticed a big chocolate cake, still completely unopened, as well as three empty dessert plates and three sets of cutlery, laid out for four people. Before I picked up the plates, I asked if anyone was expecting someone, they told me that their brother had said he would be there, and was going to have the cake, but hadn't shown up and that they had saved the best desert for him, but now he was running so late he could take it home. I asked if they wouldn't rather keep it out and eat it, and they said to me, with an expression that suggested a child who had just been caught misbehaving, that there might not be enough cake to go around. I told them I would throw it away anyway, so they should eat it, but they weren't having it. Since I was working for free, I convinced them that I should take some cake home, and they readily agreed. I took it home, ate it all by myself, and when I told my friend the story, he told me that the brother who was supposed to come was the boyfriend of a friend of a friend of his, and that the reason he wasn't there was that he had severe Down syndrome, but loved chocolate cake, and was so looking forward to it. Since then, I have avoided the quiz night, and try not to go into the town centre, as I am afraid of running into the family. Years later, and that cake still haunts me.