the owner would have to promote someone to owner in order for someone to be able to do what you want. if they’re still listed as owner, send them an e-mail. they may get it and promote a member. even if they moved, their Yahoo account could still be valid.

Yahoo’s position- which has not been updated since Oct. on this issue
Update: New Abandoned Groups Guideline

You can do the Moderator Poll in your group if the Poll feature is On. With the Poll results, write an email to group Tech Support and they will promote the elected member as the owner or moderator.

URL of the Support help form: