What is strange about saying Was it a car or cat I saw?

Cars and cats are very different things, so it's unusual for someone to be unsure about which one they saw. Typically, people can easily distinguish between a car and a cat. Additionally, the sentence doesn't make sense from a grammatical standpoint. It would be more accurate to say, "Was it a car I saw, or was it a cat?" or "I think I saw a car, but it might have been a cat."