I think it is possible to get knocked out in a car just from the jolt of the cars movement without even hitting your head.
I have known spirits to take on a physical form, and move things in your house open doors etc and maybe your mom hit this spirit with her body, spirits have also been known to intentionally hit others, there is a lot of strange stuff in the world we do not know about yet. I have a theory that a spirit could send to a person a telepathic signal that could disable them, or control them, in the Bigfoot world they are calling it infra sound, but I think Bigfoot and Dogmen are demonic spirits that take on a physical form also which are causing people in our woods to go missing.