Where did my Sim's cat go?

This question is a little similar to another in this site, so the solutions are also similar. You either did one of three things:

(1) Accidentally click the "Put up for Adoption" which basically deletes the pet. Solution: If its deleted, you will have to buy another one. Check each household to make sure.

or

(2) Relocate the cat to a different house than you intended to. Solution: Again, check each household.

or

(3) Relocate the dog to a house, and the cat is just hiding somewhere. Especially, in the larger lots and in more complex houses, the cat is usually hidden from view. Unlike dogs, cats can actually use stairs and elevators (even teleporters) and they may be upstairs. Solution: Navigate the camera in the household as they can be tiny and hard to find. A quick check would be to buy a cat bowl and have a sim do the action "Call Over" using the item. If the cat is in that house, then he/she will respond.