The local hospital here in Fayetteville, NC just had an incident like this. A guy had fake credentials from the University of Tennessee and was hired as an ER doc. He actually began orientation and had treated some patients in the ER. He also spent time riding with the hospital owned 9-1-1 EMS service as was treating patients. They didn't get around to checking his credentials for over a month. Once they found out, he was arrested. However, he posted bail and then skipped town. The only way they knew he left town was after a taxi driver called the police and told them that some young kid got into his taxi and told him that he was a doctor and that he needed to pick up a patient and have them transported to TN. When they covered the story on the local news, they had a big picture of him standing in front of a local ambulance wearing the EMS uniform that was issued to him. It was definitely a blow the hospital.
For those interested, here's a link to the story:
http://abclocal.go.com/wtvd/story?section=news/local&id=7805604
Scary.