GWS to the injured rider.Great that so many people stopped to help. Must be scary for you as the leader of the group - no-one wants an emergency when they're in charge!
A bit odd that no-one else in your group noticed his absence - if I was riding in a group I'd hope that everyone was looking out for everyone else.
In my ladies group we usually ride one leader in front one in the back if it's anything more than half dozen riders.
In a large group being the only leader is too much responsibility imo.