On November 29, I published an article entitled "Google Investigating Missing Files on Drive" at https://eogn.com/page-18080/13285158.  You might want to read that article first before reading about "the fix" below:

Just install the latest client and follow the instructions, but don't ask questions.

Google has released an updated version of the Google Drive app for Windows and macOS that, along with some simple manual work, should resolve missing file issues.

A help page was published by Google yesterday that includes steps to resolve issues with missing files for "the small subset" of Drive for desktop users it said were experiencing the glitch. Per the company, affected users should install the latest version of Drive for desktop, which should be version 85.0.13.0 or newer.

Once installed, Google said users should run the app, click the Drive for desktop button in their menu bar or system tray, and while holding the Shift key, they should click Settings, where "Recover from backups" should appear. Click that to start the recovery process. 

Users should then see a notification saying that recovery has started, followed by recovery being complete, though be prepared to wait. Any files and folders that are recovered will show up in a new desktop folder (i.e. not in your locally synced Google Drive space) titled Google Drive Recovery.