In 1891 he does seem to be the only Robert Chapman of that sort of age in Smallburgh RD
In fact he may be the oldest Robert Chapman in Norfolk.
I wondered if he might have died in the Smallburgh workhouse/infirmary.
However, the Robert Chapman who died in Smallburgh in 1897 seems to have died in the appropriate sub district for Hickling (Ludham)
Page 39 in volume 4b is the first page of Smallburgh deaths in Sep 1897. Ten names, with apparently only five indexed on page 40 (presumably end of sub district)
(Same thing with Mary Ann Chapman in Dec 1890 and Robert junior in June 1893, both indexed on the first page for Smallburgh in those quarters)
Looking at the others on page 39 in Sep 1897, burials for eight of them can be found in the parish registers online.
Emma Trorey, age 74, buried 20 July, Hickling
Henry Ready, 88, buried 22 July, Waxham, of Gt Waxham Rectory (Hickling) - he was the Rector
John Beevor, 62, buried 27 July, Potter Heigham (abode Catfield)
Caroline Dack, 60, buried 13 Aug, Stalham (abode Catfield, late Stalham)
Four were buried in Ludham
Mary Rouse, 38, buried 7 July
John Knights, 73, buried 12 July
Elizabeth Crane, 63, buried 22 July
William Grapes, 69, buried 19 August
So it looks like it ought to be your Robert who died in Sep qtr 1897, either in Hickling or somewhere very nearby indeed. The absence of a burial record is strange!