At the White House, few aides outside the East Wing have known Mrs. Trump’s whereabouts, and her office has kept the West Wing — which tends to leak like a sieve — on a need-to-know basis after the first lady returned from a five-day stay at Walter Reed National Military Medical Center in May. In the absence of answers, theories about Mrs. Trump’s health and the length of her recovery have abounded. Her aides have held firm, citing the privacy laws to which Mrs. Trump, like any other patient, is entitled.

And when that does not work, they have admonished journalists for inquiring.

“Mrs. Trump has always been a strong and independent woman who puts her family, and certainly her health, above all else, and that won’t change over a rabid press corps,” Stephanie Grisham, the first lady’s communications director, said in an email on Monday. “She’s confident in what she is doing and in her role, and knows the rest is just speculation and nonsense.”

Aside from the reception on Monday, there have been few reported sightings of Mrs. Trump in the White House. A reporter said last week that he caught a glimpse of Mrs. Trump walking with her aides through the West Wing. In recent days, Mrs. Trump has taken internal meetings and is planning events, her spokeswoman said, but her office has not shared updates on when the first lady might resume her public appearances.

Mrs. Trump’s absence came abruptly, and at a time when she seemed to be getting used to standing firmly in the spotlight. She was admitted to the hospital just days after the kickoff of Be Best, her official platform. In the weeks before, the first lady had organized a state dinner with France and saw her poll numbers rising.

Then she vanished — not an easy feat for someone whose every public move has been dissected on social media.

“It’s amazing she’s been able to pull it off given the scrutiny that first ladies are under in our times,” Ms. Jellison, the historian, said. “For all we know, maybe she does understand what the expectations are but just chooses not to play that game. This particular first family and this particular White House has their own road map for doing things.”

Questions about Mrs. Trump’s health and whereabouts are likely to persist, particularly since Mrs. Trump has not traveled with her husband. She did not accompany the president and several of his grown children to Camp David last weekend, and the East Wing confirmed that she will not travel with Mr. Trump to the Group of 7 economic meeting in Quebec this week, or the summit meeting with the North Korean leader scheduled to take place in Singapore next week.

Ms. Grisham, the first lady’s spokeswoman, dismissed curiosity about her travel, saying that it was “pretty typical” not to travel after a medical procedure.