Isn't it possible HKS just said she ate an omlet when she really did not? Or KE made it up?
Well, if it wasn't in her stomach, it was surely in her intestines. I suggested eatlier that perhaps someone else ate it. I would have if it was going to go to waste. The other choice is that it got flushed down the john. Matter does not disappear.
But now the harder question, why? Surely they knew that an autospy would be done. Did they already think they had Perper buttoned up at that time?