Photoshop is hidden and won't reveal itself

Intermittent problem: Adobe Photoshop window will just refuse to display.

Running: macOS Sierra 10.12.4, and Photoshop CC (2017), both up to date.

iMac intel core i7, 32 GB of ram.

Photoshop is running, but won't show itself.

I have a document open and unsaved, but cannot see any part of Photoshop except for the menu bar. If I hit Command-Q, I'll get an unsaved document dialogue, but still cannot see Photoshop.

None of the menu commands seem to help: I have tried a few in Window > Arrange > Consolidate to Tabs, and others, to no effect.

I hide all other apps and check all spaces and the Photoshop interface is nowhere to be found.

When I right-click the Photoshop app icon in the dock and choose "Show All Windows" I just see the desktop with a "No Available Windows" message.

Photoshop where the hell are you? I have work to do!