I think i just found a cat tooth on my floor?

i have 2 cats that are over 3 years old. i have only been in this house for a year. i was just sweeping my living room which is wood floor and found tooth. but it wasnt a human tooth it was small and kinda curved. I am guessing it was from my cat but they were over 2 years old when we moved her. and i have read that they loose their teeth at 3 weeks. so why would I be finding a tooth of a ful grown cat.