That's the problem. Clicking on "Default for Display" will make it visible - provided I have a microscope to read the small type. To me that's a bug that can be worked around.
I'm having exactly the same problem today on a Mac Mini running Sierra. I *am* using "default for display" (which is 1080p for the display I have hooked up). There is no "native" Apple screen for a Mac Mini. The restore button is nowhere. The uploaded image is a full-screen screen-shot.
I desperately need to retrieve these old mail messages and their enclosures. (Files are one thing, but has the poster who wrote "do it by hand from the backup volume" ever tried to recover mail messages and their enclosures by hand?)
There's no menu bar available, so that workaround is out. Does anybody know of any "keyboard shortcuts" that activate the buttons in Time Machine?
Sigh. I Remember when Macintoshes "just worked." At this point, I'm fully expecting a fall Apple announcement for a "zero-button mouse" to complement their new zero-button Time Machine.
[doublepost=1500841392][/doublepost]Oh, this is precious. I honestly don't know whether or not to feel stupider than the guy who programmed this user-hostile UI.
If your Mail window happens to be set to occupy most of the height of the screen, the image of that window in Time Machine will COVER the Restore button! If you make the window shorter, then invoke Time Machine, the button is visible. Similarly, you can resize the large window smaller while within Time Machine, and the buttons will appear. Having done so, you can no longer resize the window to cover the buttons again… but Time Machine fails to make the same check at time of invocation to determine whether the buttons are covered.
Curiously, it DOES perform this check for Finder windows and adjusts their size... but not Mail windows. Even more curiously, temporary image flashes suggest that it DOES shrink the Mail window just before throwing up its main display, but then displays the original unshrunk version anyway. That would lead me to suspect that some of the other special "inside the app" Time Machine cases (like Contacts, iTunes, iPhoto, etc.) may exhibit the same problem.
I don't remember which release replaced the "big black bar at the bottom" with the current modest translucent buttons (probably the same one that removed that god-awful remote-service-hostile animated Star Wars background image), but I suspect the big black bar never let itself be covered.
Three weeks of coffee duty are strongly indicated for somebody in Cupertino.