Need Help Deleting Paperwhite Files

Having searched numerous forums, I now realize I did a bad thing - deleted books and documents from my Kindle Paperwhite's "documents" folder using Windows Explorer across a USB link. Too bad Paperwhite doesn't come with a warning not to do this. I thought it was fine because that's how I sideloaded the mobi files to the Paperwhite "documents" folder, as these were not Amazon purchases. Now, no matter what technique I use to "delete" these books, including touchscreen delete menu and Reset Device, they always reappear in my Paperwhite's "documents" folder when I turn it on - presumably because their sidecar files are restoring them.

Note - these books are not stored on the cloud and they are not detected by Manage Your Content. So where are these sidecar files, and how can I delete them to keep these books and documents from constantly being restored to my "documents" folder? (BTW - Kindle tech support is useless - the techs I have spoken with are clearly not "techs," merely working off scripts with no intimate knowledge of the inner workings of the Kindle file system.)

Thanks for any help!