This is one of the weirdest issues I had come across. On my Virtual Machine, I wanted to look for an error message in the output window and I pressed Ctrl+F to search for the text. I can see the SSMS windows getting greyed out but the Find and Replace window does not appear.
Instead of the shortcut key combination, I tried Edit –> Find and Replace menu item. Same result. Then I started going back in time. What had changed? Couple of minutes back I had changed the Screen Resolution of my VM and I had SSMS open at that time. In fact I had lowered the Screen Resolution. Now I know the reason why the Find dialogue is buried somewhere in the screen. Since I had lowered the resolution, Find dialogue was still in its original position and it was not visible with the current screen resolution.
How to fix this issue? SSMS has an option called Reset Window Layout. Clicking on this option would reset the positions of all windows within SSMS.
Just one click on this option and I could see the Find and Replace window right in front of me!