By the time you read this, the mystery of Steve Fossett's disappearance may already have been solved, his remains found in the wreckage of a light aircraft somewhere in the woods of California.

If not, be warned: the conspiracy theorists are going to have a field day.

Within hours of the news emerging yesterday that Fossett's pilot's ID cards had been found in southern California, the blogosphere was alight with speculation, rumour and half-remembered fact. Steve Fossett? Oh yeah. You mean the guy that faked his own death?

Fossett was last seen as he took off from a secluded Nevada airfield on September 3 last year to scout for a suitable site for a land-speed record attempt. Conditions were perfect and as one of the world's most experienced aviators, the 63-year-old record-breaker did not bother filing a flight plan before setting off in a single-engined craft known for its reliability.

His disappearance sparked the biggest search and rescue effort in US history. The Civil Air Patrol sent up Black Hawk helicopters with heat-seeking equipment, the National Guard committed its own search crews and dozens of other aviators inspired by Fossett's record-breaking feats scoured thousands of square miles of desert, canyon and scrub.

Backing them up were tens of thousands of websurfers trawling fame-by-frame through Google Earth satellite images in an unprecedented attempt to ally "human intelligence" with computing power.

They found nothing, or at least nothing that gave any clues as to Fossett's fate. The search was called off a month later and on February 15 a judge in Fossett's home town of Chicago declared the missing adventurer legally dead.

Not everyone believed that to be necessarily true, however, including Lieutenant-Colonel Cynthia Ryan, the official spokeswoman of the Civil Air Patrol, who made her doubts public in a newspaper interview in July.

"I know very few people here, friends in law enforcement, who buy this story like the rest of the world has," she said. "I've been doing this search and rescue for 14 years. Fossett should have been found.

"It's not like we didn't have our eyes open. We found six other planes while we were looking for him. We're pretty good at what we do."

News reports suggested that Fossett may have been living a double life before his disappearances. One mistress emerged, then another. One report suggested that the multi-millionaire trader had made some disastrous investment decisions.

Another expert to raise doubts was Robert Davis, a loss adjuster who spent several months investigating Fossett's disappearance for Lloyds of London, the reported underwriters of a $52 million life insurance policy in Fossett's name.

"What I've strived to find out is: what happened to this man in the run-up to his disappearance? Why did he disappear?" Mr Davis told reporters.

"I spoke to people who were on the scene, people who were helping out with the search efforts, anyone whom I thought could shed some light on this. And what I discovered is that there is absolutely no proof that Steve Fossett is actually dead.

He added: "I'm not a conspiracy theorist, I'm a man who deals in facts, and I don't really care if he is alive or dead. It makes no difference to me. What I am interested in is the truth - and a proper criminal investigation of this man's disappearance was never undertaken by law enforcement or officials in the state of Nevada."

Fossett's pilot's licence, two other ID cards and $1,005 in cash were found tangled in a bush off a trail near the town of Mammoth Lakes by Preston Morrow, a ski shop manager, on Monday. He turned over the items to local police on Wednesday after trying unsuccessfully to contact Fossett's family.

A local Sherrif's department spokeswoman said last night that there had been an aerial sighting of possible wreckage, although she refused to pinpoint the location.

In the meantime, the conspiracy theorists got to work. According to Lieutenant-Colonel Ryan, a California Highway Patrol officer had reported seeing Fossett's plane near Mammoth Lakes on the day he disappeared, but police had never been able to trace the officer. Did he never exist or was a crucial clue missed?

Times Recommends

• ‘Thousands of Tamils dying’ in Sri Lanka camp
• Jackson 'rebuilt his nose before he died'
• Tehran: militiamen attack protesters