It looks like Yahoo Messenger for iOS was released on December 3: https://itunes.apple.com/us/app/yahoo-messenger-chat-share/i...
And apparently there's a native OS X client coming, as well: http://mashable.com/2015/12/03/yahoo-messenger-is-back/
And apparently there's a native OS X client coming, as well: http://mashable.com/2015/12/03/yahoo-messenger-is-back/
It's still mystifying that there was no iOS or Mac version for such a long (albeit temporary) period of time.
Also mystifying that I apparently deserved a -4 for this comment. Seems valid to me to note Yahoo not having an app on iOS or Mac OS for well over a year.