Not too long ago, I went into Fungus Grove on the world map to fight the boss of the area, during that time a Myconid invasion was going on for it. When I went in and explored to fight the boss, I fought Myconid instead, I did a few more battles thinking that once the raid was over, it would go back to where I would encounter the boss. When I clicked away from the world map to do something I realized that a task was done when I looked at the explore tab, It was the quest for defeating the bandits in Fungus Grove. When I went to Fungus Grove again to make sure I could encounter the boss again, I couldn't, and it went to the camp searching event instead. I'm not sure if this is a known glitch or something, as when I went scrolling through the threads of bug report I didn't see anyone else talk about it, but I'm adressing it just in case.

The zone events that pop up in the MotD banner are shared site-wide events. So it would just mean that other players had completed the event and that it ended.

The events spawn every 3 hours though, so you will definitely see it again at some point. =)