I have a MacBook Pro with two external monitors connected. I also use Spaces, so I have three displays visible at any time, and a couple of virtual desktops, and a couple of apps running full screen.
Every now and then Chrome will pop up a dialog somewhere that I can't see - sometimes it's off the screen, sometimes it's hidden behind another apps window, and sometimes I don't know where it is. If you don't find it and dismiss it, Chrome won't allow you to close tabs or windows, minimize or full-screen a window, or close Chrome.
Sometimes I can get the missing dialog back with some combination of command-tabbing between apps, or using F9 Expose to show all the displays. The "Show All Windows" option in the Dock icon never works. That's how I know what's causing the problem. But sometimes I can't find it for love nor money. When that happens, the only solution I've found is to Force Quit Chrome using option-click on the Dock icon.
Is there a better way to find this errant window?
(I had a look at How can I find alert-type dialogs that prevent other windows of the same application to be focussed? and those solutions don't work either.)