To avoid this, Never: Move, Rename, Delete, or Add a file or folder from outside of Lightroom. Always do file operations from inside of Lightroom or it will have no idea they ever happened.
Also, make certain that you don't allow Drive letters to drift by connecting external storage devices in different orders or combinations without having permanet assignments to their drive letteers made.
When you repoint by clicking on the Question Mark, it should find adjacent missing files. You can also do the same operation for missing folders in the Folders Panel which might corral more of them.
