In no way does the FIC prepare you for what happen to them.
There have been plenty of instructors put in the same position ended up in the same boat.
There is some bits of instructing which can be simulated and other bits just smack you between the eyes when they first happen. And its usually the students/pilots who you think are pretty good which bite your bum the hardest.
When they do happen its up to the individual and their own ability's to sort it out. Having a current FI ticket doesn't really change the situation.