A fee years ago, I discovered that if someone was running dual monitors and using XScreenlock, you could unplug one of the monitors and it would bypass the lock screen. I have no idea if this is still possible, I've not used XScreenlock since then.
On Windows 10, if you have dual screens and unplug one while the screen is locked, it will reconfigure the displays and give you a flash of what was under the lock screen. Hope you didn't leave anything sensitive on your screen!
