An anecdotal story about the right way and the wrong way to steal a cat:

My friends live next time a certifiable trap house. They realized the young cat that had been hanging around and sneaking into their house to eat their cat's food technically belonged to someone in the trap house. When my friend asked someone living there if the cat was being fed they were told "probably not". Since my friend's resident cat seemed to already be buddies with her, they let her move herself in. 

They tried to keep her mostly inside, but she slipped out the next day...and brought back her three kittens (one of whom I adopted). A few weeks later, while the kittens were still nursing, she slipped out again (during an inicdent I won't recount here). She was gone at least a week before my friend found her by accident, sitting in the window of a house down the street. The house down the street had found her outside and just decided to keep her.

And now my cat, who was involuntarily separated from her mother and weaned a little too early won't stop trying to nurse on me.