Originally posted by Renlish:

The only other thing I can think of is that you missed a raid event of some description, but if that had happened, it stays active until you return to the place it started so you would have known.

That's not 100% accurate. I had a main base up on a hill and a smaller port base a short distance away. The port was completely surrounded by an earthen wall so there was nothing the trolls could destroy there and eventually the troll event spawned while I was there and I just sprinted away and left it go thinking it would just stay there and I could do other base building things without another one spawning.

It worked great but after 3 game days the event ended on its own even though I had stayed on the other side of that island the entire time.