I cant quite remember but I think there is sort of a metal wedge cork shape that the bolt screws into inside the bar and the inside of the weight is split so that the wedge /cork spreads out the split section and what has happened is that the wedge is still in there tight. Screw the bolt back in part way and then give it a tap with a hammer and that should push out the wedge, then you can pull the whole lot out with the wedge still attached to the last few threads of the bolt