I'm pretty sure SFMI has spent quite a bit of time (and money) trying to track down the present owners of those claims that have been idle since the 1800s. I guess at some point if you can demonstrate that the heirs/owners can't be determined or found that you could file a claim for the rest of the claim. While I think that SFMI would keep their acquisition of new claims quiet to prevent others from getting the idea to file claims on the mountain, they'd have to be pretty open about any title action- though they wouldn't necessarily put out a PR. But I would imagine they'd have to file some kind of public notice before being able to acquire the remainder.