How would your job find out if you die in a car crash on the way there?

They would eventually be notified by police or family members.

When you didn't show up, they'd call your home.  If you don't live alone, the person living there with you would probably have been informed.  Short of that they would probably find out from news reports.

Usually from next of kin, or whoever ended up linking you to x job, or they just read about you in the obituary one day.

If someone calls them about it.

I honestly don't know. 

Fortunately for me though, I can walk to work in 5 to 10 minutes.

Assuming my brother didn't die in the crash with me he would let them know