With great appreciation,
FYI ~ I have a wonderful spell in the Supermarket Sorceress to help pets get along and a very effective ritual in PowerSpells to find a lost object. And you are right, there is also something mentioned in The Encyclopedia of Magickal Ingredients. You can use a magnet to hold up a picture of your cat on the altar or even on your fridge. This will help magnetize the other ritual and draw the cat home.