iOS 18.2 deletes files and restores from old backup

Well, you should consider backing up more frequently, and, as the instructions for the update told you, you should make a backup before any update.

The best strategy is to turn on Automatic Backups, and that way you can only lose one day’s updates.

If you synced data to iCloud you can resync that back to the phone.

Everything disappeared because iOS crashed during the update, and had to be restored. Rare, but it happens.

But you have just provided more information that is very valuable. Email and notes (and Calendars, reminders and contacts) sync to an email account, so probably whichever email account you are syncing to was logged out, and you have to log back in.

Go to Settings/[your name]/iCloud/Backup/iCloud Backup and it will tell you when the last backup was; then tap on Back Up Now. Wait until it finishes, and if it fails it will tell you why. The most likely reason is not enough iCloud storage.

You can check that under Storage at the top of the iCloud page (Settings/[your name]/iCloud). If it is full tap on it and then Change Storage Plan to “rent” more storage.

Automatic backups happen when the phone is powered on, the screen is locked and the iPhone is connected to power and Wi-Fi. The best practice is to charge the phone overnight, every night to assure the backup will happen.

By any chance, did you back up your files to your computer or to iCloud before performing this update?

davedma wrote:

It is supposed to automatically back up to iCloud but it’s now decided to say the iCloud storage is full! Also how can you follow instructions on an update when it does it automatically overnight with no prior notice?

Turn off automatic updates. But that aside, you are asking for trouble if you don’t back up frequently, as often as you have new content that you don’t want to lose. This isn’t the only thing that can go wrong; you can drop the phone, or drop it in a toilet, or throw it under a bus, or it can be lost or stolen.

iCloud comes with 5 GB free; you can increase that to 50 GB for 99¢ a month, and to higher capacities for higher fees, but 50 GB is enough for most people. And, as I said, you can turn on automatic nightly backups, and also sync data to iCloud (which is different from iCloud backup).