Sotheby's did not release details on the buyer, but reports said the winning bid was made by telephone.
But Branczik said: "You could argue that the work is now more valuable".
The artwork, "Girl with a Balloon", from 2006, was auctioned at Sotheby's auction in London last night, when it "self-destructed".
"The unexpected incident became instant art world folklore and certainly marks the first time in auction history that a work of art automatically shredded itself after coming under the hammer", the auctioneers added in the statement.
Many are suggesting that the piece could actually increase in value following the prank. Sotheby's refused to reveal who had bought the piece before it was shredded.More news: Interpol president reported missing during trip to China
A rare piece of artwork from Banksy went up for auction this evening - only to self-destruct moments after it was sold.
"Banksy did it again to the art market that he so despises", he said.
"It appears we just got Banksy-ed".
Other recent works included the opening of Dismaland, his dystopian, Disneyland-esque theme park in 2015, which he described as a "family theme park unsuitable for children". The spray paint and acrylic on canvas that was mounted on board depicted a small girl in black and white reaching out towards a red, heart-shaped balloon attached to a string.
Banksy's real identity is unknown, though most accounts say he comes from Bristol where he started out as a small-time graffiti artist.
He rose to fame with graffiti that appeared on buildings across the United Kingdom, often marked by deeply satirical undertones.