I'm glad you asked about the mysterious Private Robert Stevens. I went back to all my sources for this raid and his name doesn't seem to appear in any of them--just in my compilation note card for this event. Further, of the nine troopers in the 4th Cavalry MSM named Stevens or Stephens, none seemed to be named Robert and all nine are accounted for at the time of the 1 Sep 64 Tipton raid. I found three Robert Stevens listed in the MO State Archives online military service records, and none of them seems to match this soldier either. It looks like I flat goofed, as I cannot account for where I got this man's name. Sorry.
Based on this, it appears that both Joseph Fuller and Mr. Gabriel died from their wounds at Tipton.