Ms Sheehan, who has become a standard-bearer for protesters against the Iraq war across the United States, left the roadside camp late on Thursday after being told her 74-year-old mother, Shirley Miller, had suffered a stroke and was in hospital. More than a hundred supporters of Ms Sheehan remained at the site in Crawford and spirits rose when they heard that she intended to return soon.
Mr Bush did meet Ms Sheehan, 48, briefly late last year soon after her son, Casey Sheehan, a military mechanic, was killed near Baghdad. Since then, however, she has stepped up her campaign for a complete withdrawal from Iraq, demanding a fresh meeting with the President.
She pitched her tent in Crawford on 6 August and vowed to stay there until Mr Bush met her or until 3 September when he finishes his holiday and returns to the White House.
On Thursday, Ms Sheehan and the other demonstrators walked the four miles from their campto the President's ranch to deliver 200 personal letters to the President and his wife, Laura. Most were written by parents who have lost sons and daughters in Iraq. A White House official said every letter would receive a response.
Ms Sheehan's quest has received intense media attention and it seems to have struck a political chord that is beginning to unsettle senior Republicans. Polls now show a majority of Americans think the invasion of Iraq was a mistake while the President's approval ratings half-way through his second term are at historic lows. On Wednesday night, thousands of anti-war activists staged candlelight vigils across the country to support Ms Sheehan.
Chuck Hagel, a Republican senator from Nebraska, urged Mr Bush to meet with Ms Sheehan as soon as possible. "I think the wise course of action, the compassionate course of action, the better course of action would have been to immediately invite her in to the ranch," he told the CNN news channel. He argued that most Americans were now comparing Iraq directly to Vietnam.
But not everyone looks so kindly on Ms Sheehan. Some groups accuse her of casting shame on the US military. Supporters of the war and of President Bush drove in a convoy past the protest site, triggering fears of a weekend confrontation. And the conservative group Move America Forward has unveiled a new TV advert designed to counter the Sheehan message. It features the group's founder, Deborah Johns, whose son is a marine in Iraq. "I'm here to tell you that military families support our troops AND their mission - in spite of what people like Cindy Sheehan say," she says.
"Cindy Sheehan certainly doesn't speak for me, our military families or our men and women serving in Iraq and Afghanistan."
Casey Sheehan was sent to Iraq to help maintain its fighting vehicles. Aged 24, he was killed when he tried to save fellow soldiers during an ambush by insurgents last December.