Put collars at your cats at home and do not let them go outside unless they are on a leash.
Our indoor-outdoor cat learned to love to go camping, go for walks on a leash and be tied up to sit with us by the fire.
Whenever we came into the TT after being gone without him, we opened the door very carefully and were ready to grab him. We never had to be after ten years we never stopped being ready to grab him when we opened the door.
One of his favorite times was just before we went to bed and we took him for a walk around the park. He would go to the door and say clearly that it was time to go for a walk. As we approached the door he would go sit on his leash so we would remember to put it on him.