The campaign by the government of President Corazon Aquino to retrieve "hidden wealth" spirited abroad by deposed president Ferdinand Marcos is part crusade and part treasure hunt, according to investigators and diplomats.

Aquino has said that she is determined to recover what she considers looted government property from Marcos and also set an example to Filipinos long tolerant of corruption in high places.

For the handful of veteran "Marcos-watchers" who for years kept books on his apparently labyrinthine financial dealings, the campaign is also a chance to act on the detailed information they say they have amassed at considerable risk to their own safety.

For those whose anti-Marcos credentials are questionable, the campaign has been a way to demonstrate loyalty to the Aquino government.

Delighted by the return of a free press for the first time in 14 years, half a dozen revitalized Philippine dailies are following, and often printing, all the leads and tips related to the investigation.

After years of whispering rumors in coffee shops, Filipinos are volunteering what they consider to be information, although it is often undocumented and unlikely to stand up in court.

Almost every day produces front-page allegations charging that Marcos, his wife Imelda, and associates made off with a bundle in smuggled gold, stashed billions in Swiss bank accounts or sought to buy the Reagan administration's support.

Today, for example, the official audit commission disclosed that its inspectors found $2.75 million missing from Manila Airport funds in January and suggested that Marcos may have used them in his reelection campaign, which has been estimated by analysts in the Philippines and the United States to have cost $250 million to $300 million.

Although the sum involved was relatively small in comparison with other allegations of "ill-gotten wealth" obtained by Marcos and his associates, the disclosure was unusual. Audit chairman Theophisto Guingona produced for reporters the documents and a check demonstrating that the funds were sent from one government agency, but never received by another, as intended.

Almost all the other cases were reported, often as mere leads, to the recently established Commission for Good Government, which is investigating misuse of public finances under the 20 years of the Marcos administration.

Run for the most part by volunteers, the understaffed commission makes no secret of its inability to verify most of the incoming torrent of leads and documents.

Yet mere confirmation that the commission has been notified often has been enough for the local press to print a story unsubstantiated by evidence. Or, as one anti-Marcos investigator said of the local newspapers, "It's a different kind of journalism; some use stories others judge still at the rumor stage."

Often local press stories are then picked up by the foreign media.

Such was the case this week of the charges in the Philippine Daily Inquirer that Marcos had sought to curry favor with the Reagan administration with plans to spend $67 million on Republican campaigns in 1980, 1982 and 1984.

The man who distributed the memorandum containing the allegations, denied by U.S. officials, admitted that they "did not meet U.S. journalistic standards."

While not excusing that case, Eduardo Sanchez, a journalist turned successful investment banker who prides himself on being an early "Marcos-watcher," invoked what he called a "coincidence of interest."

"We are looking for the money stolen from our country, and journalists are looking for good copy," he said. "It's a treasure hunt."

"The real problem is that you can have volumes of documents in court," he said, "but still not have the missing link."

Privately, some sources close to the Commission for Good Government expressed fears that they may be involved in a gigantic fishing expedition.

Most of the Marcos fortune, they suggested, may be based on seemingly legitimate investments made years ago on funds skimmed off and sent overseas.

Sanchez conceded that Marcos may retain most of what he stashed abroad. But he thinks that the investigators could get lucky and that the current campaign might just persuade bureaucrats and others in the know to come clean.

"With good luck and psychological pressure," Sanchez said, "we hope to smoke out the big guys thanks to the little people who've been caught and might turn state's evidence and lead us to something bigger." In the view of some Filipinos and foreigners, there is also a touch of national emotion and wish fulfillment to the campaign.

"There's an understandable reluctance to see Marcos and his cronies enjoy the fruits of their ill-gotten gains," a sympathetic western diplomat remarked recently, while cautioning that the present mood might "engender some unrealistic expectations about what can be recovered."