The 28-year-old's coach Dave Alloway has revealed that the Team GB captain was "devastated" by the tight decision, which he felt that he had done enough to take.
"It was a close fight," said Alloway. "The Mongolian was a very good operator, but [Tom] gave it his best shot.
"He's devastated because he wanted to win a medal in his home Olympics. He's trained so hard for it, so to be one point away from a medal, one scoring blow, that's what hurts."
Uranchimeg will now face Ukraine's Denis Berinchyk in the semi-finals tomorrow.