RE: sametime persistent chat in mobile client Ben Williams 17.Nov.14 05:02 AM Lotus Notes Sametime Mobile 9.0Windows
That feature is available via Sametime Advanced (server side component) but I'm certain that the mobile client doesn't support that kind of functionality. I have never tried my mobile client with Advanced in the mix but I doubt whether the mobile client works in that way. Sametime Advanced isn't used as widely as other Sametime components so I doubt whether it has been built into the app.
You could use a meeting room as a persistent chat room. Meeting rooms can keep the history of all chats, documents, polls etc that have occurred within it.