How do I undo "svn switch" on a subdirectory?

Not for the first time, I've accidentally done "svn switch" from somewhere below the root of my project. This switches that subdirectory only, but how do I undo this? If I try switching the subdirectory back to the original branch I get: ``` "svn: Directory 'subdir\_svn' containing working copy admin area is missing" ``` Update: I've got changes in the subdir, so I don't want to do a delete. In the short term I've fixed it by reapplying the changes, but I was after a way to get Subversion to re-switch back to where I came from... or is this a missing feature?