Matt48, well said.
For us, this would be similar to studying the escape routes of the hotels we stay at on overnights. One day it might save your life.
As for the mystery blade, looking at the remaining fan, my guess is it went out the front or through the inlet cowl. There seems to be very little damage to the remaining fan. One adjacent blade bent? The previous incident showed massive damage. Either the blade went forward or it slid cleanly between the remaining blades and out the back of the engine.
Something caused the cowl to self destruct. Blade, vibration, what ever, hopefully the investigators can learn what so it can be prevented in future.
As for the window, something hit it. Once again, I'll leave it to the investigators.
Finally, great job by the crew on a really bad day.