Right, because those scientists were psychic? Neutrino observatories look for neutrinos continuously. They do not throw away data, if there are neutrinos detected they will be logged. Never in the long history of neutrino observation has there been a spike in detections similar to what was observed with SN 1987a. Moreover, that observation heavily confirms our pre-existing models of neutrino generation and behavior in Type II supernovae.
