If the example is crucial to the word you are looking for, let's examine it a bit more closely
A: Hey, I remember that car with the scratch from the crash last week, you must be the one who caused it.
B: Are you sure? It didn't necessarily have to be me, I see a car with a scratch like this almost every day.
So, the crucial point is that 'a car' is used by B to mean 'some car'. However 'some car' in this context, as an argument that helps the statement that "it didn't have to be B" can only mean "a car that is not B's car". Therefore this is not just a deceit, I would still call this a lie (alternatively, it is a contradiction).
There are many definitions of a lie, I don't object to the one given by wikipedia
A lie (also called prevarication, falsehood) is a type of deception in the form of an untruthful statement, especially with the intention to deceive others.
Untruthful is defined as 'not honest or true' in macmillan.
Combining these two definitions it really is not crucial in the given example if the statement can be interpreted by someone as correct representation of reality; what is important is that the statement is not honest and has an intention to deceive. (However, I tried to show in the opening paragraph that the argument can not even be taken as something based on truth).
Wikipedia entry on deceit has the following categories:
- Lies: making up information or giving information that is the opposite or very different from the truth.
- Equivocations: making an indirect, ambiguous, or contradictory statement.
- Concealment: omitting information that is important or relevant to the given context, or engaging in behavior that helps hide relevant information.
- Exaggeration: overstatement or stretching the truth to a degree.
- Understatement: minimization or downplaying aspects of the truth
Under this classification you can say that it is equivocation ('a car' is taken to mean 'some car other than mine' and 'my car' at the same time), concealment (the fact that this 'some car' is actually mine is hidden) and understatement (to refer to 'my car' as 'some car' is an understatement). Finally, even under this classification you can call it a lie ('a car' is made up, it is actually 'my car' and saying 'a car was stolen' or 'my car was stolen' is very different).