When you move an asset that has been freshly created and not yet saved, it will leave behind information that will get saved by Save All. This saved data isn't visible in the editor but is present in the Windows Explorer. This can cause confusion with using Source Control.
Regression?: No
This also occurs in 4.13.2
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-39869 in the post.