So if it could be an inadvertent squeezing trigger as the shooter STARTS to lean over then perhaps the Z143-45 movement of SS agent Hickey may indicate it was at that point which a bullet was fired.
So the angle of the rifle is not dependent on the Z frame point in time because the angle of the rifle as the shooter is holding it while he is in transition to placing it on the boxes could have been much less acute than would be if he had aimed a shot at Z143.
Therefore that angle was perhaps a lot less acute , and thus the bullet could have ricocheted off the asphalt and was the “something” that Virgie Rachley saw striking the pavement.
The bullet must still be somewhere in Dealey Plaza.
Going with Murphys Law that if an object is dropped it will roll into the most inaccessible part of the room and adapting that to a bullet fired at 2000 ft/sec striking at a slight angle to the asphalt pavement and the “room” being Dealey Plaza area, that the most inaccessible area would be drain/sewer pipes.