You don't know what could have happened if you were with your friend in that ride. Maybe both of you returned home safely, maybe both were involved in a terrible accident.
When I was hit 3 months ago, I was 10 mins late due to a flat. I thought, if I hadn't flatted, that car wouldn't have hit me. But then thought that maybe 10 mins earlier a truck could 've hit me head on (happened to a cyclist not long ago, the truck driver got asleep) and I could be dead.
No sense brooding about "what if" in these cases IMO.