safari bookmark folders disappeared on its own

Hello all you wonderful helpers! 🙂

A few months ago, I went to bookmark a website in Safari to a folder I use often. This folder was somehow no longer there. It seemed to have disappeared on its own. I did not have time to figure it out then.

Today I went to bookmark a website to another folder and this one is gone as well. It seems a few have disappeared on their own.

Does anyone have any idea how this happens? How/can I find and restore them? Many have been here for years for research projects. Now gone, I don't know where to even begin to find all these sites.

Any help would be so greatly appreciated.

Thanks,

Michelle