maybe you could keep them shaved on the tummy and tattoo your phone number! sorry I know it's not a funny subject, it scares me too, very much. if any of them were ever to get out and got lost, I would be so upset, panicky.
no collars for my cats, but I am considering microchiping.
but the real thing that scares me, about them getting outside, is the coyotes! I lost a cat that way once. at least Im pretty sure thats what happend..