I do not recall any captive bolts on my car but my memory isn't what it should be (I forget things I shouldn't but not things I should). Are you sure they aren't captive bolts? Are you sure all the bolts either just spin or have been removed? If so the cover should come off. Do the spinning bolts come out partially and then spin? If so suspect captive bolts and look for other bolts still tight. Otherwise, sorry, no idea.