Having the same problem. Just made a new sim after the update and made a cat. She disappeared a few times, same as everyone else, no warning that she ran away, can't find her on the lot, doesn't have the adventurous trait, whistle doesn't work. I got her back a couple of different ways: if I traveled somewhere else, traveled with her, or exited the game and came back she would be in the house. I just got her back from the vet and locked all the doors. When she completely vanished again with all doors locked I realized it must be a bug. It's seriously stressing me out because this cat is based on my own LOL. I've had other issues with cats in the game before this recent update, like one basically forgets she has a litterbox and won't use it, or cries for food when the food bowl is full and I still have to call her to eat. That cat runs away all the time even though she always has food and a clean litterbox and 4 sims in the house to pay attention to her. I wondered if that was a bug as well. I just have pets and the magic expansion so I'm really frustrated that there are so many issues with pets.
