I have a A3 Umidigi smartphone, Android 9. I downloaded the images by Google Chrome (search images engine), and I can't find them in any folder (included Download, Pictures or DCIM), but I can see and use them as backgrounds (actually I use as background one of these downloaded, invisible images). I searched them using the App "Total Commander" (and other similar), and I connected the smartphone to the desktop by usb cable, but I couldn't find them. Google Chrome has access to the drive. Now, if I download another picture, Chrome asks me where to save it, but I have a dozen images I can't find.
In the folder
/data/data/com.android.chrome and its subfolders, would be the place to look. You will need superuser permission to be able to access this folder. In Total Commander start File System Root.
/data/data/com.android.chrome/cache/image_cache Has picture files. Actually all the files in there are pics even though they have no extension.