I am having a similar issue for the past week, Android 9, but do not have cloud storage turned on in Google photos. Mine happens when pictures are taken and held in local memory and can be seen initially from within the camera app, but don't seem to be read by Google photos and then are wiped from even being able to view them in the camera app. I had recently updated and now have another so maybe there is a patch to correct the issue or a bug that has not been identified yet. I am thinking of trying a different photo viewer app to see if the issue is related to Google Photos or the camera.