ther should definately be a bolt holding the rotor bracket on, they some times crack in half from fatigue, did you look inside the hole and verify there wasn't a bolt? did the independent shop forget to put it back or was it already missing? normally when a rotor is replaced you do not need to remove the rotor bracket. the plastic part is designed to keep out moisture and dust, look at the picture i have attached it illistrated the area, 11 is the rotor bracket an 14 is the rotor bolt, 17 is the plastic piece. the numbers are this
bolt 104-990-05-22
bracket 104-158-04-40
rotor 104-158-02-31
dist cap 104-158-01-02

i believe i have a new ov relay for that model if you need it, let me know