Banksy took a day off — and blamed the NYPD.

The anonymous graffiti artist came up empty Wednesday, disappointing fans of his monthlong “Better Out Than In” project in New York City.

“Today’s art has been cancelled due to police activity,” according to a message posted on Banksy’s website around 11:30 a.m.

There was no further explanation, and Banksy’s publicist didn’t return requests for comment.

Rumors flew during the morning that the British prankster and two assistants had been busted by cops in Brooklyn’s 79th Precinct, which covers the Bedford-Stuyvesant neighborhood, just south of where Banksy painted a geisha graffiti unveiled last Thursday.

But the NYPD shot down the ­report, which the Web site ­untappedcities.com blamed on a commenter on Banksy’s Instagram account.

Meanwhile, a “piece of original Banksy art sculpture” — which had been lying near the since-dismantled sphinx statue erected Tuesday in Willets Point, Queens — was being ­offered for sale on eBay at the “buy it now” price of $666.69.

Seller John Mofloski, 32, of Greenpoint, Brooklyn, said he grabbed the chunk of concrete from a puddle of filthy water surrounding the work.

Mofloski, who works in video production, said he included the triple-six “mark of the beast” in the sale price because anyone who would buy the item is “evil,” adding, “I think the people that took [the sphinx] are cursed.”

Willets Point auto-glass-shop partner Elias Peña, who made off with the artwork, denied an online report Wednesday that he had sold it “to a cartel of art dealers.”

Although Peña and shop owner Bernardo Velez say they were ­offered $50,000 for the sphinx on Wednesday, Velez said he’s holding out for more and seeking advice from his lawyer because, as Peña admitted, “We don’t know anything about art.”

Velez also scoffed at the suggestion that he had stolen a piece of public art, saying: “If [Banksy] don’t report it stolen, then it’s not stolen.”

Also Wednesday, Deirdre Swords, the founder of the Red Hook Art Project in Brooklyn, said she left her business card with security guards protecting Banksy’s Oct. 7 painting of a heart-shaped balloon covered with Band-Aids on the side of a Red Hook building.

On Monday morning, her calling card was answered. The side of the Art Project’s headquarters, at Richards and Wolcott Streets, had a large rectangle outlined by four white corners with the words “Better Out Than In #Anonymous Guestbook” written inside.

Children filled the blank canvas with their own artwork on Wednesday afternoon.

“We really hope that he will come back and that the police will not punish him for coming back and responding to what these kids are doing,” Swords said.