Yes, I've seen that. Cars are often left at houses when the occupants move out. And if they left the fire burning, there would be smoke from the chimney. Also, some houses just come with cars as part of the lot, so you'd see those, too.
If your Simbot's name doesn't show up at the house he went to, he probably moved out of town. I've seen that happen many times. If they go to a lot, but don't go in the front door, they seem to just disappear and that's when they live out of town (as far as I can tell). You can try inviting him to visit and ask him to leave, then follow him to see where he goes (use the pause button to keep up).