I presume Sanders was a Tennessean, probably from the Memphis area, as that is the county in which the Tennessee company was raised. The 17th Tennessee Battalion is sort of hard to trace. I suppose this was due to its size; regiments had 10 companies, battalions usually had about half that. There is a report from January 1863, just prior to the battalion's participation in Van Dorn's Middle Tennessee expedition, that listed it as having just under 100 effectives.
I guess I can't say for certain that Sanders' three companies remained around Okolona when Ferguson's Brigade headed south at the end of January 1864. My theory seems very plausable -- the lack of mention of it in the south, that as a Tennessee unit it might have been left with Forrest as was Barteau's Regiment, and most of all the fact that Sanders was definately in the area on February 19th (the fact my ancestor was captured in west Tennessee in April 1864 might be further evidence, although it is also possible he deserted before his capture). I am currently researching another ancesteral unit. When I am done with that, I think I will try to find out more information about Sanders. Perhaps there are some memoirs someplace.
I did a history of the Weatherfords in the Civil War that I have sent to a number of people; it is also being run in a Weatherford family geneology newsletter. It is really more about the units than the family. About 50 pages long. If you want a copy, let me know an e-mail address (you can use the e-mail function on the board)and I will e-mail you a copy.