Max, I live about 5 minutes north of Bayou Chicot, the area Richard Humphries is stated to have resided at. I also try to collect and record as many Confederate graves as possible in Evangeline Parish. This Parish did not exist during the war but was carved out of St. Landry Parish. Your Richard Humphries is listed in Company F of the 8th but I can find nothing on him.
I have a book called "Looking Back; A Narrative History of Bayou Chicot" by Mabel Alice Thompson. She has no Humphries listed in her book does state in a group of names listed as having resided in the area at one time a "Umphries" family. That's all that book contains.
Wayne Cosby shows Richard Humphries in his research on Company F, 8th La Inf. but does not give a location of death or burial, he does mention the Bayou Chicot area as place of residence. You may want to contact Ms. Sue Deville of the Opelousas Museum and Interpretive Center. She is a member of the UDC and researches Confederate graves in this area. You can contact her through this page...
http://www.cityofopelousas.com/tourism_interpretive_ctr.htm
You may also wish to contact Wayne Cosby at Camp Moore Confederate Cemetery and Museum in Tangipahoa, La. I doubt though he has the grave location because we swapped info not long ago and neither of us have it. Anyway, here a link to Camp Moore...
There are at least two old cemeteries in the Bayou Chicot area that have been lost to vandalism and other reasons. One was called the Old Brick Cemetery. The other is called Cheney/Oldfield Cemetery. (I have a 2nd great-grandfather reported buried there but all the stones there save 3 have been stolen or drug off into the woods). I hope for your sake Richard Humphries was not buried in one of those two.
If you do locate his grave please let me know so I can add him to the information we have already. I will also be glad to be your legs in this area if you need me to check a cemetery or take a pic of a possible grave.
Sorry for the long reply and I hope this helps in some small way.