Robert doesn't feel bitter. It's kind of like... sour. Why were they hugging? Although, it was a very brief contact. And it looked like a purely friendly hug. Robert didn't like it regardless.
Wow. Are you jealous? You are being very unreasonable. Robert didn't even know he was capable of this kind of jealousy.
But he knows it's his own fault. He was the one who sent his friend to take his place instead.