At first, it appeared to be one of the biggest and most brazen art heists in American history.

The thieves were so professional that the wealthy victim did not even know that his multimillion-dollar Andy Warhol collection was missing until a member of his household staff walked into the dining room one morning and let out a yelp: the walls were bare.

Supposed to be hanging there were ten original Warhol silk-screens — a series of portraits known as The Athletes, including likenesses of Muhammad Ali, O.J. Simpson, and Chris Evert.

But the images, thought to be worth at least $25 million (£15 million), had vanished.

The theft last month initially sent a shudder down spines of wealthy homeowners in Los Angeles. It seemed to be yet another strike by Pink Panther-style cat burglars after a series of robberies in 2007 in which $10 million in cash and valuables were stolen from the likes of John Taylor, the Duran Duran bass player, and Sherry Lansing, the former CEO of Paramount Studios.

But then came this week’s stunning development. Richard L. Weisman, the 69-year-old owner of the silk-screens, dropped his $25 million insurance claim.

Why? Because claiming the money was too much hassle, he said.

“They turn you into a suspect,” Mr Weisman said of his insurance company, Chartis, a division of AIG, in an interview with The Seattle Times. “I’m not going to go through it for three to five years. Forget it.” For Chartis, which immediately withdrew its $1 million reward for the missing artwork, Mr Weisman’s decision brought a welcome end to the matter.

But the LAPD is proving to be less willing to move on.

Don Hrycyk, a detective working on the case, has made no secret of the fact that he remains puzzled by several aspects of the break-in. For example, there was no sign of forced entry at Mr Weisman’s Los Angeles home.

Of course, this could simply have been the result of competent thieves. But why didn’t they take the opportunity to steal some of the other highly valuable artwork that was hanging on walls nearby? And how on earth do the culprits expect to be able to get rid of such a distinctive collection?

Mr Hrycyk is also said to be baffled by how casually Mr Weisman dropped his claim to the $25 million, especially given that there was no suggestion that the multimillionaire had done anything wrong.

In addition to the ten sports portraits, the thieves also took a Warhol portrait of Mr Weisman himself — one of his most treasured possessions and a gift from Warhol for having commissioned the Athletes series in the late 1970s. There were 80 pieces originally, with Mr Weisman paying $800,000 for them in 1977. The collector later donated most of them to universities and to Warhol’s subjects, keeping only the ten that have now vanished.

“It’s a lot of money he gave up,” Mr Hrycyk said. “It’s one of the puzzling aspects you have to take into account when you do your investigation.” It is believed that Mr Hrycyk and his investigative partner want to interview Mr Weisman but have been having trouble getting in touch with him.

As for clues, there are virtually none. “I don’t have anything tangible,” admitted Mr Hrycyk. “Some people saw a ratty-looking, maroon van, which may have been parked in the driveway.”

In the world of collectors Mr Weisman is a mega-celebrity. His mother, Marcia Weisman, was one of the founders of the LA Museum of Contemporary Art and his uncle, Norton Simon, built the Norton Simon Museum of Art in Pasadena. When Mr Weisman wrote a book in 2002 entitled Picasso to Pop — The Richard Weisman Collection every high-society figure in New York came to the launch party.

Mr Weisman said that he had been left deeply shaken by the robbery, which took place when he was at his Seattle home.

“Everything in the house was untouched. There wasn’t even an ashtray overturned,” he said. “You feel like your privacy has been invaded — it’s very uncomfortable. You’re looking at empty walls with bare hooks.”

There is, perhaps, a simple reason why the thieves left no trace, he said: his alarm system wasn’t switched on — probably because his ex-wife, 16-year-old son, and household staff were coming in and out of the house at the time.

And although the LAPD has received tips on the whereabouts of the Warhols from as far afield as the French Alps (one theory has it that the works are now in a private home in Russia or the Middle East), Mr Weisman does not have much faith that they will be returned.

“Maybe if [the police] would do their job and spend some time looking for the art instead of being accusatory of the person who had it stolen, they might actually find it,” he complained to the Los Angeles Times. “The idea that I would steal from myself is the most ridiculous thing I’ve ever heard.”

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