1997 Mercury Marquis play in shift knob

It's gradually loosened up the past 2 weeks. Yesterday a brass bolt was found laying in the front floorboard. Now it will not go into park, it stays in reverse no matter how hard one pushes it into reverse. Worse it's getting harder to start, it wants to go from reverse to drive with just a very little gap between for neutral when it will start. I'd thought shift linkage at the trans but since the bolt fell out in the floorboard I'm thinking it's in the steering column. I have all coverings removed but don't see any missing bolts nor anyway to thghten this up. Help please