There's a feature named review older files in the Manage Storage option, which let's users review and delete older files. Your files must have been deleted in that way. It doesn't happen automatically and also it includes all files like mp3, mp4 and other files too not just image files.
Also if you use any backup feature either in Google Photos or Samsung Gallery ( To Onedrive ) there is also an option to clean up storage by deleting uploaded files ( Only uploaded files are deleted and also even deleted it is still shown in the apps as it is in the cloud but will not be visible in Files app ). This is also a manual process which will not occur automatically.
Your images must have been deleted in the above ways or sometimes in some other way which doesn't happen automatically.
If my comment helped you in any way, please consider hitting the 3 dot menu and accepting it as a solution. It helps me. Thank you!
Usually, photos or any media is never set to automatically delete unless you have deleted it yourself. If you are 100% sure that you never deleted it, chances are either they are still there or they've gotten corrupted and are not showing up in the gallery.
Go to Gallery and switch the view to Picture. Then all the pictures will be set according to date (chronologically). You might be able to scroll through and find the photos in the corresponding date that they were taken on.
I hope this helps you find the pics. If my comment helped you in any way, please consider hitting the 3 dot menu and accepting it as a solution. It helps me. Thank you!
