This is actually a common issue our iPhone users will meet or have experienced. For what I used ever, we can firstly check Photos app for "Recently Deleted" album. It helps keep all deleted photos and videos for 30 days. Then, it's also available to use iTunes or iCloud official solutions. It's straightforward but comes with risk to replace current data with the selected backup file. In order to pretect all data from being lost or damaged, what we can give a try is a professional tool, such as Joyoshare iPhone Data Recovery, PhoneRescue, etc.