Pretending hungry

Last Friday a real disaster happened for me. Mehrdad & I were eating lunch very relaxly and enjoy my mother delicious cooking when suddenly his phone rang and we found that his sister is waiting for us to serve the lunch. Yes, we had forgotten their invitation for lunch and already had eaten meal. But it wasn't polite to tell them about the mistake, so rapidly we dressed and go there. Obviously they had lots of meals and expected us to eat from all of them but I was totally full and each spoon I was gulping was like a real torture for me. I don't remember how those damn minutes passed but I just remember the feeling of pretending hungry although we were not. I confess that for this matter I found no way to be frank and I suffered the result.