TFS missing original files on machine

I checked some files out for edit about a week ago and I want to check them in or revert my changes. Before I do that want to see what I've changed, but when I compare them, the local copy of the original file is no longer on my machine. How can I get the original file ba开发者_JAVA技巧ck without losing my changes?

For reference, I got pulled onto something else and came back and the problem had gone away, looks like restarting Visual Studio did the job.