The starship, the USS Bozeman was the ship discovered inside of the Typhon Expanse. The TOS Enterprise spent quite a bit of time scouting and even occasionally crossing the Romulan Neutral Zone, unofficially, of course. Remember it was not unexpected for the Federation to scout the borders of their territory unofficially. Since this region was near Klingon space, it is possible there were few, if any, official explorations of Typhon space and none that were on record.ĭepending on how well known the phenomenon of the Tyhon Expanse was, it may simply have been a region marked by probes and thus known but unexplored.
Like so many things military, it may have simply been that the Enterprise was the first 'official' Starfleet vessel to chart this unexplored region.