Well pertaining to the BCV due to them being so limited, it is possible for them to hide really well. It is not like they are floating around like cabbage, the way white courts are. So in that instance, if they have been keeping their head down and not stepping on any toes. They can get by. Perhaps the BCV has friends in high places, who for helping him stay unseen, he does a few favors for them. No matter how power a supernatural heavyweight is, they would need help in some area of aspect. Nic has proven that to us when he tried to break in Hades vault, despite how stupidly powerful he is.
I feel that it would all have to boil down to the why? Maybe he is a new BCV who had a bad run in with his/her maker. An he was put to sleep for whatever reason to make him desperate, especially if he/she is new to his powers and is going on pure instinct. Time has passed him by, he's hungry, disoriented and is in need of friends to help him. Desperation can do alot to a person.