Fcuk me, if the bumper came off, did the engine drop too, or was it just the plastic bumper cover? If it was the complete bumper then that car is a death trap, as the main bolts that hold the bumper in place also secure the cross member which in turn, supports the front of the engine!

If it was just the cover, then all is not lost, except the plastic wedges that keep the cover in place. You will need to remove the rest of the bumper, (the metal chassis bit). Look in the haynes about that, because as I said, you would need to support the front of the engine to remove it. The plastic cover bit just clips into place onto the metal frame, but plastic wedges are forced into the clips from the other side to spread open the clips an prevent it from heading west under excessive braking, as yours did.