My photos disappeared

Please check the following

1. Do you have backup (iTunes or iClouds), --> Restore your iPhone, iPad, or iPod touch from a backup ...
   1. iCloud backup doesn’t include information already 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.
   2. *-If you had turned on iCloud Photos, your content is automatically stored in iCloud. 
2. Did you sync with iCloud earlier and now it is disabled. Then again --> Set up iCloud on your iPhone, iPad, or iPod touch - Apple ...
3. Have you ever imported your photos to Mac/PC --? Use Photos on your Mac - Apple Support OR Set up and use iCloud Photos on your Windows PC - Apple ...
4. Have you ever uploaded them to any Drives (OnDrive, Drive, Flickr, DropBox) - Back up iPhone data with Google Drive - iPhone & iPad ...
5. There are only three possibilities that I can think of right now...
   1. You have restored from a backup which does not have those Photos you are looking for
   2. You have un-synced your iPhone using iTunes
   3. You may have imported them to Mac/PC into Photos App and have ticked "Delete after Import"

Watch the GIF below