The supernova event of 1987 is interesting in that there is still no evidence of the neutron star that current theory says should have remained after a supernova of that size  This is in spite of the fact that many of the most sensitive instruments ever developed have searched for the tell-tale pulse of radiation that neutron stars emit
Thus, current theory is wrong in claiming that supernovas of a certain size always produce neutron stars
Several important features of the 1987 supernova are correctly predicted by the current theory.