Notes disappearing and reappearing on iPhone

So I went to check my notes that I use very frequently and every single one was gone. I tried reloading it and checking different folders and all that. I reset my phone and it was still gone then I go to write this a few minutes later and suddenly they started loading in one by one. This is so confusing and I’m glad I have them back but should I save them onto something else? Can I trust it won’t happen again? I need to be able to access and keep them frequently.

[Re-Titled by Moderator]