Trump's message in the note stood out with no mention of India's freedom movement icon, instead thanking "my great friend Prime Minister Modi" for a "wonderful visit", according to news broadcaster NDTV.
Many contrasted Trump's note with that left by his predecessor Barack Obama in 2010 in which he had written: "I am filled with hope and inspiration as I have the privilege to view this testament to Gandhi's life. He is a hero not just to India but to the world."
Prime Minister Narendra Modi was seen showing around the Trumps at the Sabarmati Ashram and telling them about the charkha. Modi also presented a memento of Mahatma Gandhi's "Three Wise Monkeys" to the US president.
Trump and Melania together garlanded an image of Gandhi at the Ashram.
The US president arrived in India on Monday for a lightning visit featuring a huge rally at the world's biggest cricket stadium and other high-profile photo opportunities, but likely short on concrete achievements.