In the version selector of a single file view in the source browser, you can select to see a file at a specific revision. If you select a revision in the past, then attempt to select the most recent again, you cannot. It no longer appears in the list. to reproduce:

• Select any file in the source browser to view
• Use the revision selector in the upper right and choose any previous revision
• After the view updates, attempt to use the selector to find the current/most recent version. It will not appear in the list.