This *seems* to be something that's just started since upgrading 16 from v1 to v2 (win 7). It's only occasional, with seemingly no particular event triggering it, and I've now seen it three times on two different hosted files (in each case hosted on different 15 servers).
In both cases, I've first noticed the issue in Browse mode, where I've checked that there is no custom menu being used. But to illustrate it, here is a screenshot from layout mode, where I can't think of any reason the status bar option would be grayed out (and keyboard shortcut doesn't work).
I just realized the situation and it was the same in 15, so I guess not a bug. There was a script at some point that did a hide toolbar [lock], and that setting maintains itself in layout mode as well. Threw me off, but appears to be expected behavior. Never mind.