It can have different reasons.
My Filou lost one of his fangs when he was 4 or 5 years old. We didn't notice it was loose and didn't notice when it went. But when we finally noticed and took him to the vet it was all purrfectly healed.

On the other hand cats can have accidents. And they can have inflammed gums. Ot tartar. In any case a tooth check from the vet would be recommended. The tartar can be removed- in many cases the inflammation of the gums is healed that way.

All the best for your furboy.