I haven't done the estimate, but if there are several people stranded, it seems to make sense to split up to improve the overall chances of survival if the odds of being found are unreliable (all eggs in one basket and such).
Please also note the selection bias, where the happy ending stories (the person who left the car quickly found and brought back help) do not get nearly as much publicity. Presumably there are public stats available, if anyone here can find them.
In every single news story that I can remember about someone getting stranded with a broken-down car, the person leaves their car looking for help and they end up dead. Or, if there are multiple people in the car, the one person who goes off looking for help ends up dead and the other people who stayed with the car survive.
My question: If I get stranded in my car somewhere, should I go looking for help? Or should I follow my availability heuristic and stay put? Since I'm still in the process of debiasing myself, should I do the opposite of what this particular mental shortcut suggests, or would that be a sort of bias bias (analogous to the fallacy fallacy)?