When special negotiator Robert Strauss took off for the Mideast in August, he carried sealed instructions.

He was displeased to discover, after he was airborne, that the orders had been signed by National Security Affairs adviser Zbigniew Brzezinski.

Strauss let the White House know, upon his return, that he expected to have his instructions come directly from the president himself.

When he returned to the Mideast last month, Strauss got another sealed envelope signed by Brzezinski. But when Strauss opened it, the only message inside read: "Have a good trip."

Nathan Landow, the multimillionaire builder friend of Hamilton Jordan, has told friends he is planning a "big party" in downtown Washington the night President Carter announces formally for reelection.

In the Polo Club the other night he was showing off what he calls his "Secret Service" pin. The little gold-and-blue lapel button does look like the one agents wear currently to identify each other quickly in crowds. It also resembles the ones White House staffers wear.

It is neither, says a White House spokesman. It is a "presidential memento," given out the way John F. Kennedy used to give out PT-109 tie clasps.

The White House declines to say who gave Landow his little status symbol, only that Jordan did not. Only senior staff aides and certain of their authorized deputies, and the president himself, of course, can award the pins.

Writing in the current issue of Inquiry magazine on the death of former CIA analyst John Paisley, the Washington Assassination Information Bureau's Jeff Goldberg quotes Paisley's wife as saying "privately" that her husband "served as a CIA contact for Nixon's White House 'Plumbers'." Maryann Paisley's attorney, Bernard Fensterwald Jr., confirms his client told him that, adding "that's all she knows . . . all her husband ever told her." Adding to the intrigue, another source working on the mysterious Paisley death says that the name of a White House Plumber was found in one of Paisley's address books, along with a telephone number that can only be dialed on the "scrambled" network that links the CIA, the White House and other sensitive phones . . .

Suzi Park Thomson has cornered the market on Korean anchovies, according to a businessman she tried to enlist as a partner . . .

The Secret Service code name currently for born-again Baptist President Carter is "Deacon." Whirlwind Amy is "Dynamo" . . .

Wearing a beret, the newly svelte Truman Capote (whose teetotal Perrier-diet regimen has melted pounds) ran into a fan recently at an airport. "Ohhh, Mr. Capote!" the fan rhapsodized. "You look just the way Audrey Hepburn WISHES she looked!" . . .

Securities and Exchange Commission investigators, in their ongoing probe of Resorts International, are now trying to interview Stephen B. Elko, the former aide to Rep. Daniel Flood (D-Pa.) who has turned into "a professional witness" in one trial after another since he began testifying for government prosecutors.

The SEC had to get in line behind GSA investigators, who wanted to talk with Elko about alleged multimillion-dollar payoffs in Pennsylvania that date back to the Nixon administration.

Elko, who just finished testifying last week in the conviction of Airlie Foundation executive director Murdock Head, expects to be in and out of courtrooms as a witness for years to come.