My Patchy was hanging out with my family when a fire broke out. Even after the fire was put out, he didn't go back to his post until I exited and reloaded. He stayed that way for about 2 days, or however long it was from the time the fire went out to the time I exited the game. He's super handy to have around. I had 3 babies and 3 toddlers and having an extra pair of hands was a real bonus.
I've never had him not return at all. I have one in another save too and sometimes it will take a few days for him to visit again but in the household with all the kids, he visits every day.