Do the rules in the "Open the first time a faction is eliminated" packet apply retroactively?
The card included in the packet covers what to do:


   The card in question reads 
 "The player controlling the eliminated faction chooses a comeback power and places it on to the blue slot on his faction card. From now on, whenever a faction with an empty blue slot is knocked out or eliminated, the controlling player chooses a comeback power and places it on to the blue slot on his faction card." These two statements are independent of each other, so the first faction to be eliminated does add a comeback power to their card.