We know from previous episodes that Angel was told by Whistler to look after Buffy. He found her in L.A and followed her when she moved to Sunnydale. So why would he be captured by The Master in Sunnydale? Cordelia wished for Buffy to never have moved to Sunnydale and it happened. But why was Angel there? Wouldn't he have been in Cleveland where Buffy was? He wasn't just randomly in Sunnydale, he moved there because of Buffy. If Buffy wasn't in Sunnydale, Angel would have no reason to be there.