A news story out of Stockholm the other day left the Western press wondering if it had been made a pawn in international oil gamesmanship and if it had unwittingly delivered a phony diplomatic message.

The startling story broke early on Friday, Dec. 5. It was carried by the Associated Press and United Press International. PetroStudies, a Swedish firm, had announced the discovery of history's greatest oil field deep in western Siberia.

The discovery was said to be of 4.5 trillion barrels of high-quality oil, double the world's known reserves, a quantity so great that it was allegedly forcing the Soviet Union to work out an entirely new plan for its own development.

The afternoon dailies carried the story on front pages, and it was mentioned by CBS and NBC on evening newscasts.

In early trading, oil stocks dropped sharply on Wall Street. So many investors wanted to sell, that some stocks delayed in opening.

In its early versions the story appeared believable. In Paris, the Soviet Geology Ministry was quoted as describing the discovery as a "unique natural phenomenon." In Stockholm, PetroStudies Director Manlio Jermol said the finding was based on very reliable Soviet information.

Later that morning and throughout the afternoon, sobriety set in. In the language of the trade, reporters started to knock the story down.

In Washington both the CIA and the U.S. Geological Survey were skeptical. A CIA spokesman said the report referred to a huge oil shale deposit at a depth of 10,000 feet that has been known for 15 years. "Only a fraction of the oil could be recovered at an exorbitant price," he said.

Brokerage houses were dubious. Merrill Lynch Pierce Fenner and Smith called its branch managers to say that the new find was improbable.

Disclaimers came even from Moscow's Ministry of Geology, where officials said they knew nothing to support the claim and had no information about the report.

By Monday, Dec. 8, PetroStudies was backing away from its own announcement. The director told AP that the report had been misinterpreted and that the field was not new. He also told UPI that much of the oil was bituminous shale and therefore non-recoverable. That bit of critical information was not in the initial announcement.

Then the story tuned enigmatic. Several early versions indicated that PetroStudies has close contacts with Soviet oil experts. On Monday, The Wall Street Journal was more explicit. It quoted Arthur Meyerhoff, a Soviet oil expert in Tulsa, who called the reserve figures ridiculous. Mr. Meyerhoff said PetroStudies is financially supported by the Soviet Embassy in Stockholm and is a conduit for Soviet propaganda. He said he had been told by a Polish Embassy official that Moscow was attempting to send a reassuring message to Warsaw. The message was that more Soviet oil was to be available to the Poles, contrary to earlier predictions. That report, according to Mr. Meyerhoff, would be believed if it came from the West.

The Swedish firm is a two-person operation. Since it was formed in 1976, it has issued six reports, all of them optimistic about Soviet oil. The last two reports have appeared shortly after discouraging studies about Soviet oil.

The Western press has to ask itself if it was used, although it can take some satisfaction in requiring only four days to put to flight a sensational story that may have been a ploy.

Still, it must recognize again the impossibilities of penetrating a story involving, or allegedly involving, the Soviet Union -- particularly in the supersensitive news of oil. And the press should regard announcements out of the mysterious PetroStudies with skepticism to the point of disbelief.