I ate his food, how EMBARRASSING.

First off I will explain who Simon is. My boyfriend's dad has a girlfriend called Jackie, she has a son called Simon. Simon a few weeks ago was involved in a motorbike accident, and has been told he probably won't be able to walk again, so he has spent some painful and miserable weeks in a special hospital. Including his birthday.

Well I went to my boyfriend's house today and his dad had cooked a roast dinner for him and his girlfriend and two other people, I had not arranged to be coming over for lunch so I said not to worry about me, and my boyfriend wasn't hungry so said he'd have his later so his dad plated it up for him ready to take.
When they all went to eat dinner, I told my boyfriend he should eat as he had skipped breakfast, and he offered me some too so I took the other plate of food and ate most of it. After everyone had finished eating his dad came through and asked if we'd eaten the food, we said yes and his dad said one of those plates was for Simon. I felt awful, and so embarrassed. His dad likes things to be organised, so instead of understanding it was an accident really looked annoyed and disappointed as if I'd we'd been greedy.
In the five years I have been with my boyfriend, his dad will cook so much food, he even cooks for me if he knows I won't be there to eat it, then he will plate it up for later. So just like any other day we took the plate of food, but this time it was for poor Simon, who is stuck in a horrible hospital. I feel bad!!! And so embarrassed. Jackie probably wouldn't have cared, and before I left today I saw there was more food made up now so it doesn't even mattter, but I just feel so bad!
Ever done something to make yourself feel really guilty or embarrassed?