Had a quick look at the UK 1881 census at lunchtime. No sign of Samuel or Mary Ann.

Then tried looking for William Stump & Ellen. Ellen Stump is there, a widow age 70, pork shopkeeper at Cliff St, Cheddar with William Spratt, age 15 and James Spratt age 11, her grandsons, and Sarah A Bull, age 6, born in the USA, her granddaughter.

So it looks as if Samuel & Mary Ann married in 1873 and by 1875 had a daughter born in the USA, who then returned to England. Were Samuel & Mary Ann no longer alive by 1881?