How to clear TFS server knowledge of my local version?

If you get specific version of Changeset "1" of your source code, TFS will delete local files, and will believe that you no longer have the latest code in your workspace. Then, when you do a get latest it will actually get the latest.

In future, instead of making a manual copy, create a shelveset. In the "pending changes" window, click "Shelve" and follow the dialogue (in this case you'd not want to keep your pending changes locally). This puts your work on the server in a secure, recoverable place, but without checking it in.

Alternatively, in the workspace dropdown, you can create a second workspace. That gives you two separate copies of the code locally, but also two separate sets of checkouts. This is really useful if you often find yourself interrupting one piece of work to look at something else.

If you do another "get specific" with overwrite, this should still fix your problem.

You could delete/remove your local workspace.

Source Control Explorer -> Workspace dropdown -> Workspaces -> Remove