Owners were warned. But I do know some owners just never alerted their group. I think all owners should have stayed on top of it reporting it to their groups . I know of one that she didn't alert anything about it
Some quiet group owners may not have known. And in many groups, a lot of people are no mail or digest; if they haven't checked the site recently, the owner had no way of letting them know.
No one can expect an owner, who after all is unpaid, to send out 1,000 emails just in case someone didn't know Yahoo was bailing.
Samdu