Issue
A folder or file in Google Drive is either missing or deleted and must be retrieved.
Environment
Google Drive Web App
Resolution
If you encountered this problem using Drive File Stream or Backup and Sync, you must log into Google Drive using your internet browser.
If the item in question was deleted, then you can navigate to the Trash button on the left side menu in Google Drive.
From there you may recover the item by right clicking on the folder inside Trash and selecting Restore. It should now reappear in its original location.
Alternatively, if your folder or file is missing and you are the owner, you can search for the name of the item using the search bar.
If you are not the owner, you can select the Shared with me button found in the left side menu. The Shared with me button will show you all the items that are shared with you. Navigate the shared items and you will find the folder or file.
To add a shared item to My Drive, you must first right click the item and select Add to My Drive.
Note that using the Search bar in Google Drive will search all items that are owned by you and shared with you.