Caves Randomly Reset.

On a server I was hosting, everyone (as in just me alone at the time) died due to a hound attack when I was fishing for goggle blueprints at the desert oasis (I couldn't escape due to sandstorm). OK that sucks, but I had marked a touchstone in case something like that happened and then I revived a little later. I continued doing stuff for a few days, grew a bunch of trees then had the bearger demolish all of them for easy wood before I killed him for meat/fur. Shortly after that I decided to head back in to the caves to refill my lantern (The first two summers I spent the whole time in the caves so I didn't feel like doing it again).

When I went in the caves to get some glow flowers for the lantern, I noticed that it looked unfamiliar. I figured I went down the wrong sinkhole or something, so I check my map to see where I was (I had explored all of the caves and a fair amount of the ruins in them) and the whole map was blank, and after a small amount of exploring I could confirm that it was not the same caves from the first 2.5-3 years on that server.

This has not happened to me before, what happened? Is it some new thing? Or some kind of error?