I just read the thing about the "misplaced car". I doubt the car was a time machine.
I've heard about things like this. People have reported 'slips' in time. Most of them can't be proven, but travel in space has been reported more than once. I read this on about a man in the 1500s who somehow ended up thousands of miles away, across the ocean, in an instant.
He was captured, and they verified that he was reported missing soon after they arrested him. That means he went halfway around the world faster than anyone could think possible, at least with the transportation available in the 1500s.
Anyway, it's not travel through time. But if that could happen, why not a woman and her son? Out for a sunday drive, perhaps, they happen into the wrong place at the wrong time, and end up in...the wrong time.
They didn't stay for long though, they dissapeard soon after the two gentleman witnessed them. Perhaps they went back, perhaps not. I haven't read any report from the 1940s that suggests they made it back.
This seems to be a common thread. Most people who report phenomenon like this say that the (plane, car, person) dissapeared soon after. Maybe this is because the object becomes "charged" soon after entering, and when it dissapated, they...whatever. Or maybe it's because that way you can't prove it, IE Good Hoax.
If I had to give a place where I think a concentration of these 'portals' would be, I'd have to say the Bermuda Triangle. There's also a Devils triangle exactly opposite the Bermuda one. This makes me think that the going ons within the Triangles are natural, since nature loves symmetry.
Now not everything that goes in the Triangles dissapear. In fact, most don't. I think that whatever 'activates' it is probably celestial in nature, perhaps depending on positions of planets, or maybe the moon.
Anyway, I've gotten so far off topic I don't even remember the question, so I'm going to wrap it up here.