I am so sorry to hear about your friends dog.
That has always scared me too.

Our little terrier is kept in the house when we are gone.

When our dogs were pups, I kept them in the house,
and when they got a bit bigger, were either
kept in the house or locked in the dog run
where it is private and secure.
(back gates also always locked)

I also make sure I had a current picture of my dogs around
and id on them. I believe in micro-chipping/ or tattoo.

Even today I always keep gates locked,
just to be safe.

People who steel someone's pet from their yard
are cruel and unfeeling.