My notes dissapeared suddenly when phone storage was almost full and icloud was not syncing

Majority of my notes were deleted of 2024, some of my notes are still there. So I bought extra storage and synced icloud and checked all email boxes linked to my notes and still couldn’t retrieve the notes. It’s a big mystery what happened to my notes suddenly. Was this because my I phone storage was almost full? But still this is a very serious matter. Photos could’ve been deleted. Why something as precious as notes were deleted?