iphone 15 pro max app folders disappeared

One possibility is that some of the Home Screens were accidentally hidden or removed. See information in Organize the Home Screen and App Library on your iPhone - Apple Support including the following:

Find, hide, and remove pages on your Home Screen

With iOS 14 and later, you can hide pages to streamline how your Home Screen looks and add them back whenever you want. Here's how to hide a page:

1. Touch and hold an empty area on your Home Screen.
2. Tap the dots near the bottom of your screen.
3. Tap the circle under the page that you want to hide.
4. Tap Done. 

To unhide a page, repeat the steps above. Then use the App Library to quickly find apps hidden on different pages.

To remove pages from your Home Screen:

1. Touch and hold an empty area on your Home Screen.
2. Tap the dots near the bottom of your screen.
3. Tap the circle under the page that you want to hide.
4. Tap the Remove button , then tap Remove. 

When you remove a page from your Home Screen, the apps will still appear in the App Library.

It’s just happened to me too. It must be a bug as my phone is brand new and this is the second time it’s happened to me in the less than 24 hours I’ve owned it.

My phone is all up to date, and restarting it didn’t bring them back.

This just happened to me. The issue is it’s showing that I have the apps in the folder somewhere on my phone when I search, but the folder itself has completely disappeared as well as whatever was in the sub folder. When I look in search and the App Store, it’s still available on my phone. I would never be able to remember everything that was in that sub folder!

Update - I restarted my phone and the folder came back?! Also found out that it was because phone needed an update.

Check your Focus settings, if your in DND mode or any of your Focus are turned on it will display only what you allowed it to in focus settings! Mine did the same thing, just turned OFF “Do Not Disturb and BOOM! Everything came back!

Hope it helps