The piece of white tissue was spotted flapping from the US president’s left heel as he climbed the steps to the president's official aircraft.
Mr Trump, who was on his way to a Make Make America Great Again rally in Minnesota, did not notice his extra baggage.
He then turned to wave goodbye before slipping inside the plane, leaving the piece of paper abandoned at the the top of the stairs.
None of his staff made any attempt to alert the president to the problem, although one of them appeared to smile and say something to a colleague. It is not known whether he was making a joke at Mr Trump’s expense.
Twitter users were quick to mock the commander in chief, one suggesting the incident “sums up his whole presidency”, while others branded him a “laughing stock”.
The president landed in Minneapolis in the afternoon and appeared at a fundraiser before heading to a rally in Rochester.
Mr Trump later tweeted a video of himself being cheered by supporters to the back ground of the song “God Bless the USA”.
During his rally speech he criticised former Minnesota Democrat senator Al Franken for resigning over allegations of improper behaviour, adding: “Boy did he fold up like a wet rag, huh.”
He ended by claiming his rise to power was ”the greatest movement in the history of our country” and predicted: “We are going to win, win, win.”
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