it most likely fell off when you pulled the rack it's common, after a while you learn how to pull the rack out without loosing the tips but **** still happens once in a while, i've lost count over the years the number of injector heat shields i have run through motors, it never feels right starting it with crap in the cylinder but have not trashed anything yet, it is plastic and shouldn't hurt anything but if you can't get it out you have a choice, pull the head or let-er rip
all america wants is cold beer warm cat and a place to take a poop with a door on it