In the span of a mere 11 days this month, $1 billion in future federal tax payments vanished. As congressional leaders were hastily braiding together a tax and spending bill of more than 2,000 pages, lobbyists swooped in to add 54 words that temporarily preserved a loophole sought by the hotel, restaurant and gambling industries, along with billionaire Wall Street investors, that allowed them to put real estate in trusts and avoid taxes. The small changes, and the enormous windfall they generated, show the power of connected corporate lobbyists to alter a huge bill that is being put together with little time for lawmakers to consider. Some executives at companies with the most at stake are also big campaign donors. The real estate provision, released on Dec. 7, is intended to close a loophole in federal law that has allowed casinos, hotels, restaurant chains and other businesses to raise billions of dollars in cash by spinning off the buildings they own into a separate real estate investment trust, or REIT, without triggering a capital gains tax payment, a potentially big benefit. The revised language drew almost no notice from members of Congress, who were given three days to review a 2,009-page spending plan and the 233-page list of tax breaks before they were asked to vote on the package with almost no debate. Three House lawmakers interviewed just after the vote said they had known nothing about it.