This is my family cat, Miss Kitty, who thinks that the phone is a kitten…
All hail the power of the lost call!
That specific noise kittens (and puppies, and most other small mammals) make is called a lost call, and it has one specific purpose: to let a mother know the baby has wandered too far away from warmth and heath and food, so she can go bring it back. It’s hardwired into mothers to respond to for a certain period after giving birth. Whatever is making the noise will get picked up and brought back to the nest – and this included the one test where my adviser screwed up his protocols and the mother dog accidentally got all the way to the tape recorder they were using for playbacks. She picked it up, not caring at all that it wasn’t actually a puppy, and set it down in her nest with the pups.
Interestingly enough, lots of animals are still very reactive to it even when they’re not actively mothering babies or after the critical responsiveness period has passed. That right there tells you how important it is to the survival of the babies to have the mom respond no matter what.
So congrats, your cat literally does think that that phone needs to be rescued and kept warm!