Two options that I can think of:
The beacons had more information than just the encoded message. There may have been star/planet maps on the beacon hulls, or coordinates hidden in morse code. Once the obvious message had been decoded, eveeyone just ran off to the planets to search.
Or, information in local Galnet at the deluvery systems for the CGs.
Yeah, looking at the beacons again might be worthwhile, but could there be other points along the way where something could have been missed?