Having taken an unassailable 3-0 lead on Thursday, England piled up 218 for five in the first of two dead rubbers thanks to Phil Salt's 55 off 35 balls and Jacob Bethell's 62 not out off 32 deliveries.
But Evin Lewis and Shai Hope put on 136 in nine overs, which was all the more astonishing after the Windies pair claimed just five runs from the first two, with Saqib Mahmood even sending down a maiden.
While the openers and Nicholas Pooran were dismissed within the space of three balls and England applied some late pressure, the Windies claimed a five-wicket victory with an over to spare.
Buttler praised the Windies after they recorded their highest successful T20 chase in the Caribbean and England's white-ball captain hopes what occurred will act as a learning curve for his callow team.
"To get 219, whatever the conditions, the opposition has got to play well," Buttler said. "Credit to the West Indies, they did. If we could have prised a wicket, it maybe would have been a different game.
"When you get conditions like this, it puts a premium on your execution and skill level. It's what you expect against top teams in international cricket - you get good surfaces and you've got to be on it.
"It's been a good eye-opener with the standards we need to have for ourselves and where we need to improve."
Bethell continued his eye-catching start to life as an England cricketer with a 22-ball fifty as the 21-year-old cracked five sixes, including three in a row off off-spinner Roston Chase, and four fours.
"He seems to have a great head on his shoulders, he seems very mature for 21, knows his game but he has so much room to improve and get better," Buttler said.
"He's only scratching the surface so he's certainly an exciting player for the future."
Rehan Ahmed also impressed with the wickets of Lewis and Pooran, in-between Hope being run out, all within the space of three balls, while he later dismissed Shimron Hetmyer to finish with three for 43.
With England's leading T20 wicket-taker Adil Rashid rested in the last two matches, Ahmed has been thrust into the position of the side's premier spinner and is rising to the challenge, according to Buttler.
"His greatest attributes are that he's confident, up for it and always wants the challenge," Buttler added. "He got us back in the game by being brave, taking risks and using his variations.
"He's done really well. It's good to see him in the side without Adil and being the main leg-spinner.
"Rash has been the most important member of our team but we need to get some games into people. Not just for Rehan but the rest of the bowling attack to feel what it's like without Adil there.
"He's always the guy you turn to and throw the ball to. Without him on the field, it gives other guys the opportunity to step up into those scenarios."
There was an end-of-term feeling to the penultimate T20 but a sparse crowd was treated to an exhibition of big-hitting with 16 sixes apiece.
Seven of them came from Lewis alone in his 68 off 31 balls after Hope's 54 off 24 deliveries kick-started the Windies charge as they eclipsed their previous highest T20 chase of 191 at home against India in Jamaica seven years ago.
They did so by extending the trend of the side who calls correctly at the toss going on to win the match to seven matches in this tour - three ODIs and four T20s.
"It's one of the first times I've seen that in the Caribbean," Windies captain Rovman Powell said. "It's very difficult if that is the case - it's too skewed in winning the toss, winning the game."