Local backup would be on the phone. But it would help to know what you mean by "force" a restore, since what exactly you are doing and what state the app and its data are in might be relevant. I've never seen anything about it promising to work after some number of hours.
I had a WhatsApp restore hang up over the weekend: changing phones, tried restoring from the cloud backup and that hang half way through copying the media. But as I had the old phone I solved that by just copying the media from the old phone via USB.
I've never used WhatsApp for SMS though, I prefer to use a separate SMS app and just use WhatsApp for WhatsApp chats, so don't know whether there are any special issues with that. There shouldn't be though, since SMS must use the standard system SMS database (distinct from WhatsApp's encrypted chats).