I too agree with Freelanceakhil, Galaxy S9 does have Recycle bin you are referring to it as a trash folder. You should look into it, you probably might find all your photos and videos in Recycle bin. You said that you haven't turned on trash it's mostly default settings. Give it a try.
Follow the steps:
- Open Gallery
- Tap on the three-dot menu and select Recycle bin.
- If you find the photos and videos in the Recycle bin long-press and select the ones you would like to restore.
- Now tap on the restore icon, and all the selected photos and videos will be restored back to your gallery.
Hope you find all your photos and videos in recycle bin. Have a great day.