You don't happen to have Offload Unused Apps on by chance?
here is a link to a article about it,
https://www.theverge.com/2017/6/7/15752132/ios-11-storage-deleting-apps-messages-photos
other then that, all I can think of
here is a link to a article about it,
https://www.theverge.com/2017/6/7/15752132/ios-11-storage-deleting-apps-messages-photos
other then that, all I can think of