You're obviously feeling guilty for not helping. Maybe next time you will, or at least offer.
In your defense, his buddies should have gone back down for him. You never leave anyone behind.
I went through something similar yesterday where I stayed with the back-end of a group of 40 because i was worried about leaving a specific rider behind. That person had a heart the size of a watermelon (metaphorically speaking) and he absolutely wanted to finish so I stuck with him pretty much all the way.
And he did finish. You never leave anyone behind.
In all fairness, I think 75% of the folks that answered yes here would not have helped.
It's too easy to say yes when you're typing from the comfort of your house.
I had a flat a few weeks ago and about 60 riders went past me and not one even asked if i had all that i needed. And yes, i had all my tools, but thats not the point here, its about ASKING and OFFERING.