Sounds like you only "know" something was up in retrospect, now that you've been made privy to that information.
I agree with your compassion for your friend's losses, not being able to hold his daughter one last time is the worst.
This forum is full of people, including you and me, who spent years trying everything we could think of to get our loved ones straight and sober, NOTHING WORKS.
Give yourself a break, and let yourself off the hook. Please.
Thanks and God bless us all,
Coyote