Check the Recently Deleted album in the Photos app
Restore from an iCloud Photos backup
Restore from an iPhone backup on a computer
Check the Files app for saved video files
Search the Photos app using the date, location, or album
Check shared albums and hidden albums
Look in third-party apps where the video may have been saved
Use Spotlight Search to find the video by filename or app
Restore from another synced device if available
Use data recovery software if no backup exists