Medieval cat

That doesn’t mean you automatically forget what a cat looks like, this isn’t a photograph it’s a painting

Yes and a painter needs it's subjects to not move. So chances are they forced the cat to sit got the fur down but once it was to the face the artist had to finish it without the animal present.

Painters typically sketch the faces before colouring. Additionally, it typically took more than one instance for a painting to be finished depending on the size. No reason why they couldn't have brought the same cat back.