Well, by removing the four bolts, you actually do remove the breaking plate/spindle assembly. The drum is attached to that plate with a 30mm nut. So just put the whole drum with the spindle back on and use those four bolts to attach it back.
If you are replacing the rear bearings, you have to unbolt the drum using that 30 mm retaining nut. You should have done it this way if you were going to replace the wheel bearing.
Also, pictures would help to better understand what you are talking about.
If you youtube on how to change the rear breaks on these cars, majority of the people remove the drum of the spindle by taking out that 30mm nut only and not removing the plate (four bolts). This is easier, however the nut can only be reused 2-3 times before it should be replaced.