Less than 28 overs of play were possible in Leeds, with one rain delay and resumption before the game was called in the first innings with South Africa 159 for two, which meant the one-day international series was drawn 1-1.
Quinton De Kock was denied an 18th ODI century as he struck a cleverly crafted 92 from 76 to help set a solid platform for the Proteas.
Buttler's England went into the final game looking to avoid the prospect of a third straight white-ball series defeat having lost five of their previous eight white-ball games this month.
After a watchful opening few overs from the visitors, England made their first breakthrough in the sixth over, with David Willey taking the wicket of Janneman Malan, just as the opening pair were looking to kick on.
Willey had been part of England's prolific and match-winning left-arm attack during the previous match at Old Trafford and struck again early, with Malan hitting the ball straight to Jason Roy on the edge of the ring to depart for 11.
At the end of the first 10 overs South Africa had picked up the pace following the early wicket and had moved to 60 for one.
De Kock brought up his first half-century of the ODI series in the 15h over, after hitting Adil Rashid for two successive fours in the spinner's first over.
His 50 came from 39 balls, including nine fours as South Africa continued to accelerate from the loss of the early wicket, having been 60 for one at the end of the powerplay, but 89 for one in the 15th over when the South Africa wicketkeeper reached his milestone.
Rassie Van Der Dussen was the next - and final - wicket to fall for South Africa just as he and De Kock had put on 75. Van Der Dussen mistimed a sweep off Rashid straight to Jonny Bairstow on the deep square leg boundary having made a measured 26 from 38.
The first rain delay came in the 21st over, with the score 119 for two because the game was reduced to 45 overs a side and the players returned to the field for just 6.5 overs before the weather intervened for a second time and the match was called off shortly after 4pm.