IPhone deleted all photos-low memory

You need to mention the exact step that you took so that someone here can help. Merely saying "They are but they aren't on my phone anymore" is not going to help.

There are several ways you can get them back unless you have intentionally deleted them.

You post does not specify exactly the process adopted by you.

If it is not in the Recently Deleted Album then either you have deleted them 30 days earlier or have never deleted any.

Please check the following

1. If you have restored your iPhone with a backup which does not contain the Photos that you are looking for then please look for correct backup on your PC/Mac --> Locate backups of your iPhone, iPad, and iPod touch - Apple ...
2. Probably you may have un-synced photos with Mac / PC, sync them again
   1. For PC: --> Sync photos in iTunes on PC with devices - Apple Support
   2. For Mac --> Sync photos between your Mac and iPhone or iPad - Apple ...
3. Have you ever imported your photos to Mac/PC and used Delete after Import --? Transfer photos and videos from your iPhone, iPad, or iPod ...
4. Do you have a backup (iTunes) --> Restore your iPhone, iPad, or iPod touch from a backup ...
5. Have you ever uploaded them to any Cloud Drives Cloud Drives (iCloud Drive, Google Drive, OneDrive, DropBox, Flickr, box, AmazonDrive, Adobe Creative Cloud etc)

iCloud backup doesn’t include information that are synced and stored in iCloud, like Contacts, Calendars, Bookmarks, Mail, Notes, Voice Memos, shared photos, iCloud Photos*, Health data, call history, and files you store in iCloud Drive.

*-If you had turned on iCloud Photos, your content is automatically stored in iCloud. 

Smart Phones neither have the intelligence nor has the hostility. Hence we need to look at our device settings and the way we synchronise our smart phones with Mac/PC/iCloud and also how careful are we in sharing our sensitive and valuable informations with friends and family members.