How do I recover missing notes after transferring to iCloud on iPhone?

Neither iOS nor iCloud automatically delete your data due to low storage. However, there are some nuances:

1. Local Device Storage (iPhone, iPad, Mac)
   1. When your device runs out of storage, iOS may stop adding new data, downloading apps, or updating existing apps.
   2. Some temporary files, cached data, and Safari website data may be automatically removed to free up space.
   3. If "Optimize Storage" is enabled for Photos or Music, full-resolution images or downloaded songs may be offloaded (but remain in iCloud).
2. iCloud Storage
   1. If your iCloud storage is full, new backups, photos, videos, and files may stop syncing.
   2. Existing files and backups are not deleted, but new iCloud backups might fail until storage is freed up.
   3. If you stop paying for extra iCloud storage and exceed the free 5GB limit, iCloud services may stop syncing, but no files are deleted immediately.
3. iCloud Drive & Third-Party Apps
   1. Some third-party apps that use iCloud (e.g., WhatsApp backups) might stop updating if iCloud is full.
   2. Apple does not delete files from iCloud Drive due to storage limits, but you won’t be able to add more files until you clear space.

Bottom Line:

No personal files (photos, documents, messages) get deleted automatically due to low storage, but system processes may offload, pause, or prevent new data from being saved.

Where were the Notes? The pic below is self-explanatory.