I have the option to warn me before closing multiple tabs selected. I left my desk for an hour with multiple windows open. When I returned, all but 1 window disappeared. I was typing on Facebook with multiple tabs open and instantly all tabs and windows disappeared without warning. No crash report either. I search for the keyboard shortcut to close a window (Alt+Spacebar+C). I tested with multiple tabs open, no warning - just instantly closed. I do not think I hit these keys by accident and I would like an option for a warning with one tab open or multiple tabs.