Oh wow, just the opposite corner of the escape button. I will try that next time it happens. Thanks so much.Of course, if it doesn't work you will hear about it. 
Rita, my apologies if you have already tried this, but typically with videos that have been expanded into full screen mode, placing the cursor near the bottom right of the image will reveal an icon that looks something like two diagonal arrows pointing at one another. Clicking on that takes the image out of full screen mode and returns control to the browser and OS
