While House is hallucinating about being on the bus and trying to figure out whose life is in danger, the Woman in Black usually appears just across the aisle from him. House notices right away she looks completely out of place on the bus, wearing expensive clothes and shoes.
The Woman in Black speaks to him and keeps asking him who she is. House keeps claiming he doesn't know.
House recreates the scene on the bus and takes Alzheimer's drugs to boost his memory. He sees the Woman, who asks him what kind of jewellery she's wearing. He answers that it's some type of resin, then finally realizes it's Amber. When he awakens from his hallucination, he asks James Wilson where Amber Volakis is and he realizes he hasn't heard from her since the previous evening. They realize she was on the bus and was one of the few people who was transferred to Princeton General and was only identified as a Jane Doe.