Sometimes if it breaks off clean you can glue it back and if clamped tight enough it will not show at all. The only thing that worries me is you said you had packed it with yellow glue, that glue might have plugged all the pores making your next glue joint not so strong. My guess is you get very little glue in the joint if you did not use a syringe. My guess is it was glued along the top and bottom edge thinly and snapped when you took the pressure off the clamp. It looks like it is following the grain line too so it should not show up too badly. Loving the Cedar top, it will be a pretty specimen.