A 71-year-old Bethesda woman suffering from a brain condition was found dazed and disoriented last night in a Lord & Taylor store in upper Northwest -- seven days after she disappeared there.

Brigitte Pierre, who vanished after telephoning her husband from the store Dec. 21, was reported in "remarkably good condition" at Sibley Memorial Hospital, where she was being treated for dehydration. Hospital officials said she apparently survived without food and water during the entire ordeal.

Pierre was found about 6 p.m. in a little-used stairwell in the store at 5255 Western Ave. NW. She told searchers that she was waiting for her husband and asked for a cup of tea.

After being taken to Sibley, the woman told medical personnel that she had slept "almost the whole time" she was missing, a hospital spokeswoman said. She was admitted to the hospital last night to restore her fluid balance.

"We're just thrilled that she's alive and that we found her," said Robert Morrison, regional vice president of Lord & Taylor. "We're ecstatic. It's like a Christmas miracle, I guess."

In the hours after she was found, mystery continued to surround Brigitte Pierre's whereabouts during the last week. Store personnel had looked at least twice in the area where she was found, Morrison said. He said it was unclear how long she had been in the stairwell.

The woman's husband, Henri Pierre, said last night that "we were considering the worst."

This Christmas was to have been the first in 15 years in which the couple and their three children, who include a daughter who lives in Paris and a son who lives in London, were to be together.

With Brigitte Pierre missing, he said, "we did our best, but it was a sad occasion."

A missing persons report issued by the Montgomery County police described Pierre as suffering from Alzheimer's disease. Her husband denied last night that she suffered from the disease, but described her as "very confused" and "very forgetful," and said that she was found three months ago to be suffering from "shrinkage of the brain."

He said she had always telephoned him after he took her for her regular hairdresser's appointment at the Western Avenue Lord & Taylor, a few blocks from their home in Bethesda.

On Dec. 21, he brought her to the store about 10 a.m. and at 11:15, as usual, she telephoned and arranged to meet him in front of the store. But this time, when he arrived, she was not there.

Police were called and store personnel were notified.

"We started looking around," said Morrison. "By Monday night we had made a thorough search of the building." The next day, he said, they made an "extensive search . . . and Wednesday again."

The Dec. 23 search, he said, probably involved "every nook and cranny " of the two-story, 170,000-square-foot building.

Brigitte Pierre, a regular customer, was well known to store personnel, Morrison said. No unexplained movements inside the building triggered hidden alarms. There were no signs of unauthorized exits or entrances. Morrison said store personnel looked in the area where the woman was found "at least twice." Had she been there all week? "We don't think so," he said, but she "was there today."

He said the stairwell is in a relatively little used, employes-only area, in a back corner of the builiding, and that, normally, there is "no reason why any of my employes would go back there."

The hair salon where Pierre had her appointment is on the second floor of the building. The route to the stairwell from public areas on the second floor, he said, passes through a 30-foot-long corridor marked "employes only."

In the wake of mounting frustration, the D.C. police department's missing persons bureau decided to search the store once again yesterday. Police said two 2nd District officers, Valna McFadden and Karen Moss, found Pierre sitting at an unused desk in the stairwell.

"She was there, looking very disoriented, asking for a cup of tea," Morrison said. "She said she was waiting for her husband to pick her up." Although Pierre "looked very disoriented, she walked out of here on her own" to an ambulance that took her to the hospital, Morrison said.

A physician said that an elderly person with relatively low caloric needs could survive for many days without food or water, particularly if inactive and permitted long periods of sleep.

Married since 1942, the Pierres had lived in Paris under the Nazi occupation during World War II. Henri Pierre had joined the French newspaper Le Monde immediately after the Liberation. Now a free-lance contributor to Le Monde and other publications, he had been a Washington correspondent for the newspaper in the 1950s and again in the 1970s.

When the good news came yesterday, Henri Pierre said, "I was overwhelmed with joy." Staff writer Rene Sanchez contributed to this report.