I’m using VSCode version 1.52.1 on MacOS and I had a similar problem that may not be the same problem, but I’m guessing it will work for you as well.
When you’re in the Explorer view, in the upper left part of Explorer you have your “Open Editors.” If that shows a dot to the left indicating that the buffer has changes in it, you can right click the file name and select “Compare with Saved.” This will open another buffer to the side that will show you any unsaved changes.
To get rid of that window (it took me a bit to figure this out I’m sorry to say!), you can click the ‘X’ to the left of the extra buffer in “Open Editors.”
Hope this works for you!