Why would you need to know "how many people have been hit from 'elsewhere' and simply walked away... in order to detrmine whether being hit from elsewhere is much more likely to KILL you while you are cycling than is being hit from behind in daylight?
In order to determine "likelihood," you need to determine the aggregate… This is typically done in the insurance business and is known as “actuary,” or the analysis, evaluation, and management of statistical information.
All your current data says is that more people do die in collisions from “elsewhere,” but it does not determine “whether being hit from elsewhere is much more
likely to KILL you.”
The data to determine that is missing. You may be more likely to be hit from elsewhere, but the likelihood of dieing is indeterminate, based on the data available.