But that's what I'm pointing out in my original comment... Cats definitely experience love, they notice the absence of people or animals they love, and they react to it.

All I'm saying is that I don't think the word "grief" is the correct word in this context, because grief implies an understanding of the concept of death, which is a very human idea that we had to learn. We weren't born with this understanding, learning about death is something very upsetting that children have to go through.