Castiel watched over the Winchesters like he had promised, even though sometimes it hurt to see Dean. He watched as their father enrolled them in a school during a hunt. Dean didn't bother this time, not with any of it. Castiel wondered, and bitterly at that, if that was because there was no Robin there to impress. He watched the older Winchester brother bunk off school, as well as get himself another girlfriend. Another replacement for Castiel.
This one was called Amanda, and they seemed pretty serious. She asked him to meet her parents, but Dean didn't want to. Maybe he's not as in love with her as it first appears, Castiel pondered.
Then Dean was caught cheating on her with some other girl, and their relationship was over. The angel wondered why the Winchester acted the way he did, kissing other girls as though it were nothing and not working. Amanda had said it was a front for his 'pathetically sad loneliness.' But Dean wasn't alone. He hadn't been alone since the day Castiel first met him. Surely Dean knew that?
Sam Winchester was faring well too. He had had some conflict with a bully, and Castiel had thought to step in, before deciding against meddling further into human affairs where he did not appear to be needed.
They left the school, eventually, moving on to another town, another case. Another chance for Dean to hook up with more girls, more replacements. It was as though he was trying to get through as many different people as possible, to wipe the imprint of Castiel's lips from his own. But why would he do that? Was he ashamed?
Castiel flew down to Earth one night when Dean was alone, giving Sam advice on how to talk to girls.
'Hello Dean.'
The other boy turned around to face him. 'Jesus, Cas. It's been a while,' he said awkwardly.
Castiel looked him over. He looked different in person, more tired. 'Yes.'
'How have you been?'
'Are you ashamed of me, Dean?' Castiel asked, ignoring the question directed at him.
'What? Why?'
'You kiss all these other girls like you kissed me, but more,' Cas explained. 'Are you trying to forget me?'
'No, Cas,' Dean said. 'I just… What we did should never have happened. I took advantage of you, and I'm sorry for that.'
'But Dean-'
'Drop it, Cas.'
Castiel stopped and looked at the floor forlornly. Then, with a flutter of his wings, he teleported back to Heaven.
Dean prayed to him, prayed for him to come back , to talk. Castiel didn't want to. So he didn't. He went to Balthazar to check on the garrison, and then he went to ask if Gabriel had been spotted anywhere. the archangel was still missing, and Castiel wondered if he should pray for help. He tried it, desperately, but got no answer. The other angel was the only one he could go and talk to, and as he wasn't there, Castiel had to suffer alone.