I noticed your posting, because I have frequently seen the Maddox name in my Bartholomew County research.I don't find any connection to my family (Maddox is not in my direct lines), but I recommend you watch for that spelling when you are searching in the area.I don't live there now, but I was born in Bartholomew County and my family lived in Clifty Township.
1880 (online transcription from LDS familysearch)Clifty Township, Bartholomew Co IN pg 18b Maddock, Robert B md m w 38 farmer ENG ENG ENG Ruth E wife md f w 36 kh IN IN IN Clara M dau 15 IN William F son 13 IN Thomas O son 10 IN Isabelle dau 6 IN Sarah M dau 1month IN Maddock, Robertfather wd m w 71 gardner ENG ENG ENG
From Bartholomew Co death records & Bartholomew Co Archives: Clara M Maddock married Isaac N Wiley 9 Feb 1893 Bartholomew Co IN William F Maddock married Matilda Jane Hook 15 April 1888 Bartholomew Co IN Thomas O Maddock married Martha J (Marty Jane) Emmert14 Nov 1898 Bartholomew Co IN Emma I/J (Bell) Maddock married Harry R Emmert 17 Sept 1893 Bartholomew Co IN Sarah Maddock married William Beatty 1 Dec 1905 Bartholomew Co IN
(Quite a few births are listed in Bartholomew records for Robert's grandchildren; note that on some of these records the name is listed as Maddox)
Regarding your specific question--
Bartholomew County deaths show: Robert Maddock, male, white, age 81 d 6 Sept 1890 Bartholomew Co IN Robert Maddock, male, white, age 61 d 17 Jan 1905 Clifty Township, Bartholomew Co IN
There are 2 listings in the Bartholomew County Archivesfor Little Sand Creek Cemetery (Grammar, section 27 of Clifty Township, Bartholomew Co IN), so it might be that both Robert Jr & Sr are buried there: Robert Maddock, Little Sandcreek Cemetery, page 2 Robert Maddock, Little Sandcreek Cemetery, page 3
If you are not able to locate someone to go to the cemetery, you might contact the Archives Dept to see if they already have a reading--they are quite helpful in doing lookups in their records.With the exact date, the Bartholomew County Public Library will likely be able to find a newspaper notice as well.
Best of luck.
P. S.I noticed that the Indiana mg index shows the following, which seems a little odd: MADOCK JONATHAN TILBERRY HANNAH Huntington3-2-1843 TILBERRY HANNAH MADOCK JONATHAN Huntington1-4-1851
1850 index shows Jonathan Madock in Huntington Co IN, 57th District, page 57; Robert & William B are in Springfield Twp, Franklin Co, page 371; and there is a Galon Madock in 2nd District, Ohio Co, page 333. Under the Maddock spelling:Eli in Wayne Co IN; Nathan in Cass Co; William H in Morgan Co.