At the end of the car chase scene in The Terminator, the titular villain makes an escape and isn't seen until later in the film.
Watching that scene, there's 35 seconds between when he hits the wall and when anyone looks over to see he's gone. In that time, he could have exited the passenger door and casually walked away.
Presumably he was damaged, which would explain why he didn't immediately continue the attack. But he wasn't stunned or anything. He spends 3 seconds assessing the situation and decides to temporarily flee, then he climbs out the door facing away from everyone and takes a hike.
And there's another overturned car just past the police car, and darkness not far beyond. Fleeing without being noticed would have been pretty simple.
Update: He was damaged, yes. I think the next scene after this is where he's in a motel room repairing his face (I could be misremembering). Heck, if he hadn't been damaged, there's no reason he wouldn't have immediately pressed the attack. But he wasn't knocked unconscious like a human might have been. He had plenty of time to assess the situation and decide he needed to flee, and step out the passenger-side door.
The car he hit just before the crash was overturned there, so that'd provide cover for the first dozen feet or so of fleeing. After that, as you can see near the end of the scene, the street-lights end and it gets dark. Can't see exactly where, but he might have had only a few feet to go to reach darkness. And he was wearing dark clothing.
After reaching darkness, there's a street to flee on.
And if you watch the scene, every single cop was focused on the couple in the car, on the guy holding a shotgun. It's easier to flee if nobody's looking at you.