There were no yellow ribbons, no popping champagne corks yesterday in the Dupont Circle hotel room, overlooking the sunbathers and bongo players, where Peggy Say's prayerful hopes turned to frustration, anger and despair.

Say's brother, Associated Press Beirut bureau chief Terry A. Anderson, was not in that Red Cross convoy that led the 39 TWA hijack victims to freedom in Syria. He was nowhere to be seen -- and no one mentioned his name -- during the dramatic press conference at the Damascus Sheraton, where the freed Americans praised the support of their compatriots and the compassion of their captors.

Anderson was one of the seven they left behind.

These seven -- the "forgotten hostages" -- were kidnaped in isolated incidents over the past 16 months. In addition to Anderson, they are David Jacobsen, administrator of the American University Hospital in Beirut; William Buckley, a political officer at the U.S. Embassy; the Rev. Benjamin Weir, a Presbyterian minister; Thomas Sutherland, dean of the agriculture department at the American University; Peter Kilburn, a librarian there; and the Rev. Martin Lawrence Jenco, head of Catholic Relief Services in Lebanon.

During the diplomatic maneuverings of the last two weeks, the fate of these seven became linked to the fate of the 39 TWA hijacking victims. President Reagan and Secretary of State George P. Shultz in their public utterances reinforced this linkage, declaring that "all 46" hostages must be returned. But the intractable morass of Lebanese politics ultimately forced the administration to accept the 39 TWA hostages without the earlier kidnaping victims.

After the 39 were released yesterday, Reagan told the nation and the world: "Let it be clearly understood that the seven Americans still held captive in Lebanon must be released along with other innocent hostages from other countries."

Shultz, too, insisted at a press conference that the administration still demands the release of the seven.

Privately, a senior administration official told reporters that the United States probably made a mistake in linking the seven kidnap victims to the 39 others in the early days of the crisis.

For the families of the seven, there had been an initial rush of optimism, an intense and welcome glare of media attention. But now, they fear, there may be a return to obscurity for America's remaining hostages.

"We're disappointed. We're even depressed," said Andrew Mihelich, a nephew of Jenco. "We would have loved to have seen them in the background shots, we would have loved to see them get off that bus in Damascus . . . To us, the event is not over and the government has not failed us yet."

But if the intense administration and media attention subsides now, he said, "we will resume our aggressive and active family approach to keep the plight of the original seven in the media, so they do not truly become the 'forgotten seven.' "

Peggy Say's long wait reached an emotional peak in the early hours Saturday, when a State Department official telephoned to say "we have reason to be hopeful" that her brother could be among the Americans expected to be spirited out of Lebanon to Syria. She flew from Batavia, N.Y., to Washington and waited. On Sunday the 39 TWA hijacking victims were freed. Her brother and the other six were not with them.

"I made a big mistake," she said through tears. "I have a tendency to believe what the State Department tells me."

Now Say's agonizing odyssey, which began when Anderson was kidnaped in Lebanon last March, and which brought her to this fourth-floor hotel room overlooking Dupont Circle, is about to take her into Beirut's Shiite slums.

"I'm going to Beirut," she declared yesterday, after watching the hostages' press conference on television. "I'm going to Beirut to bring my brother home. . . . If it takes something rash to bring Terry home, I'm going to do it. I think it's shameful I have to do it."

Jean Sutherland, wife of hostage Thomas Sutherland, spent yesterday watching reports of the hijack victims' release and waiting for the telephone to ring. Sutherland, too, received a midnight telephone call Friday from a State Department official, who expressed guarded optimism and told her "when we have any news, we'll be calling you back."

That was midnight Friday. And as Jean Sutherland listened for news of a breakthrough, watched hostages disembarking in Damascus and saw the interviews with joyous family members, her anguish continued.

"Not a single word," she sighed yesterday. "We're still going on the same thing we were going on for 2 1/2 weeks, and that's no word."

Despite the avowals that the seven would be included in any release, Sutherland said she was never optimistic. "Even though we were really encouraged to know we were being included on this side by American officials , Nabih Berri the Shiite Amal militia leader had never given any kind of intimation that there could be any inclusion over there."

Still, she remains hopeful. The release of the 39 sets a precedent, she believes, and has opened the door to negotiations.

"The release of 46 was the demand, and it's been backed up by Reagan," she said, "so the crisis is not over. I don't think it's going to be allowed to be forgotten. The attention is just too great. It may go into a quieter period of negotiations, and that may be okay. I really have faith."

As for the hopes that were raised and so quickly dashed, Sutherland was not discouraged. "That's what we call the Beirut philosophy," she said. "We hope a lot and we expect nothing, so we're never disappointed."