I have lost several years/events of photos. I cannot find them in the cloud either. Is there any hope of finding them somewhere?

Alternatively - you may be opening a different library from the one containing your picturs.

Hold down the option key while starting photos. Is more than one library listed? If so, open each in turn to see if they contain your missing pictures.

What did you do to loose them? You should b able to restore them from your Time Machine backup.