There have been and there are private parcels of land in the wilderness that predate the formation of the wilderness area. There is still a private dude ranch in Yellowstone Park. Some where along the timeline of the ownership, the Federal Government will obtain the right of first refusal from the present owner. The owners usually think at the time that they will never sell or their family or the corporation will never sell. Owners die, corporations change and the parcel in the wilderness or National park does not have any sentimental value to them, just money to be collected by the sale. Once the government buys the property, it is theirs to do with as the wilderness management plan dictates. Even if the current Ranger on location wanted to keep the buildings or airstrip on newly purchased private property, they have to follow the management plan. That was the issue with the picnic tables at the Moose Creek camping area. Even though it seemed like no big deal to have a few picnic tables, the Ranger was just following the plan in place.
The Forest Service is mandated to review periodically how they manage their assets within the laws in place. That is why they have public input on how the areas are used and managed. It is vitally important that we give input as users. The RAF has been diligent to provide input. It's too bad they weren't around 40 years ago. I was on the last "official" trip into Gates Park in the Bob Marshall Wilderness to haul out a tractor after it was decided to close a beautiful recently upgraded airstrip.
While at Johnson Flying Service as a youngster, we flew the DC-2 into the Moose Creek Ranch with some of the last freight before it was officially closed. The buildings had just been burned, but the outfitter was allowed to service his booked clients out of tents until the hunting season was over that Fall. Then the Moose Creek Ranch was no more. I talked to the principal owner/operator that day and he was very sad/mad. In the case of the Moose Creek Ranch, his corporation decided to pull the plug.
Anyway, a long explanation as to what happens to those private holdings. If we didn't all own planes, maybe one of us could buy one of those parcels.
If you want to go to the Silver Tip Ranch in Yellowstone, the Park Service owns all the surrounding land so no motor vehicles will get you there. You will have to go in a horse drawn wagon from the road.
Bob