A fractured cribriform plate (anterior skull trauma) can result in leaking of cerebrospinal fluid into the nose and loss of sense of smell. Smell plays a large role in the perception of taste. So, in practice, a patient may complain of loss of taste rather than of smell.
It can't be the Facial nerve, physical examination was normal. Someone would probably notice the face symptoms.
I went with Glossopharyngeal, but that wasn't it.