A few accidents!!! Oh well a few people have died there are a little over 6 billion people on this planet we can afford to lose a few fellow diver's!! NICE!! Glad you are so compassionate. Good for you.
9 deaths in 12 months at a location which probably sees tens of thousands duing that time period is statistically irrelevant.
OTOH, 1 death in a decade amoungst a groups of friends is absolutely devastating.
What happened was tragic and traumatizing to everyone involved. In the aftermath of these things we always seem to find comfort in laying blame.
There were several points in the timeline leading up to this loss than 1 person doing the right thing could've prevented the whole episode.
1) Shop noting he was only OW Cert and prohibiting him on a 100ft plan.
2) DM limiting the dive to 60ft because 2 of the divers wouldn't go deeper than 60ft.
3) OP convincing the friend that he can always go to 100ft after he has logged a few more dives.
4) Diver remembering the PERSONAL RESPONSIBILITY FOR HIS SAFETY that is part of PADI Training and deciding to dive within the limitations of his training.
A lot of assumptions are made, the DM knew he was missing & continued the dive. Remember the DM also knew he had at least 2 divers who chose not to dive with the main group. What if he though the man was staying with his friend & fiancee? In that case he never would have know the diver was missing. Maybe the underwater exchange was him asking you if the guy was missing and he thought you knew but were okay (as if you knew he had surfaced solo or something).
As someone lese said, the 3 sides of the story: Your's, Their's and the truth lying somewhere in between.
Half of my 10 dive in the Philippines were with an instructor as my buddy (was taking AOW) so he was specifically my personal buddy. The other half I was part of a group with 1 or 2 DMs accompanying. We always had a buddy and the DM was a tour guide.
At any point if I wasn't comfortable I was ready to call the dive for myself. In fact I discussed my high SAC witht he staff and together we agreed to jump me up to a larger tank. As a diver I'm active in planning my dives.
When I hit the beach in Subic Bay I only had 8 logged dives but still I understood I was the responsible for my safety.