Missing 20,000+ photos and videos after creating a new Apple ID

If there are no backups and no local photos and no iCloud Photos usage, then there are no photos.

If iCloud Photos was in use, then the photos are associated with the Apple Account. Log into the (old) Apple Account at iCloud.com, and check for photos there.

20,000 photos with no backups is unfortunate. Most of us have learned about the necessity for backups by losing some or all of our data, though that lesson can be a tough one.

lost_photos227 wrote:

what I'm not understanding is where the photos went. If they were on her phone and she didn't delete them, where are they?

Your daughter and the Apple Genius involved might have a better idea, but we’re at a remove. We don’t know.

The “having issues with her phone”, and a lack of backups, and switching Apple Accounts, provides opportunities for data loss. Or for data misplaced.

Check iCloud.com, logging in there with the old account. Look for photos, and also look for a backup stored in iCloud.

The act of creating a new Apple Account (formerly called Apple ID) would not in itself delete photos. But this was very likely followed by some action that did erase the photos.

MrHoffman’s response is exactly correct.