lost note in note app

I kept an important note in the notes app all year, adding details to it frequently. Most recently I added to it in October. However, the note has now disappeared from all of my devices. It's supposed to be on my phone, my i-pad and my lap top as well as the i-cloud, but now it's nowhere to be found. I've tried all of Apple's suggestions to retrieve it, but nothing has worked. Can anyone offer a solution?