It might be considered an Act of God.
I just did some quick web research on it. If a sinkhole damages your home, it is like an earthquake — your normal policy excludes it. But you can buy a rider or a separate policy to cover building damage or loss caused by sinkholes. Texas and Florida require insurance companies to offer sinkhole insurance.
What I didn’t find is what happens if your entire LAND just disappears. This isn’t uncommon along sea cliffs. Every few years, coastal erosion wipes out cliff land in California...along with the houses on the land. In many places, the value of the land far exceeds the value of the structure.