I don't think your SST fragmented. I used to hunt with a 300 winchester magnum and in 2008 I shot a buck from about 25 yards with a wins heater 150 grain power point. It entered the front shoulder quartering toward me exited the second shoulder and lodged in an iron wood tree behind it. Funny thing is I found two exit wounds but both shoulders were broke and the insides of the deer were mush. Needless to say it was a bang flop.
My point is these bullets are not designed to flat out penetrate. They are designed to give rapid controlled expansion. Expending almost all its energy while giving acceptable penetration. Also I believe that your 30-06 is slow enough plus even if that bullet did frag on impact there is still 165 grains of bullet travelling at whatever your speed is and would likely cause massive trauma and a very quick kill.
Not trying to call you out but I would tend to believe that the shot was not placed correctly. Like I said if that bullet f ragged on impact it dumped 100 percent of its energy into the deer.
Also the SST is a design not so different from the Remington corelokt.