Safari bookmarks folder missing and bookmarks moved unexpectedly

This morning I opened Safari and my bookmarks folder named "Weather" was missing, i.e. had been deleted, which I did not do. I found my weather bookmarks in my "Webcams" bookmark folder. I also did not move those bookmarks to that folder. I had to create a new Weather folder and individually move each of more than a dozen bookmarks into that new folder. Why is Safari moving these where I don't want them and deleting the original folder?