Fu Yuanhui suffered a "heartbreaking" defeat to Brazil's Etiene Medeiros in the women's 50m backstroke at the world championships on Thursday as one hundredths of a second cost her gold.
Medeiros clocked 27.14 seconds, a new Americas record just 0.08 away from the world record, while China's Fu had to settle for silver at just 0.01 back.
Fu became a social media star at the 2016 Rio de Janeiro Olympics after a video of her smiling, having been told she had won joint bronze in the 100m backstroke, went viral as she struggled to contain her emotions.
But her tears of joy in Rio were juxtaposed by her bitter disappointment in Budapest at missing out on a gold medal as she wept in the mixed zone.
"It is a heartbreaking result, I tried my best, I was swimming not just for myself but for my coach, my friends, my family," said the 21-year-old.
"People know me for laughing, but if they see me crying they will be very sad, so this time I will go home before I cry.
"I prepared very hard, I thought I had prepared enough, but I don't know why it didn't work out as I had expected."
Ironically, in the semi-finals, Fu had also been just 0.01 seconds behind Medeiros, the fastest qualifier.
Having won silver over 50m at the Kazan world championships two years ago, the 26-year-old Medeiros went one better in Budapest having also come within 0.12 of the world record on Wednesday.
She says a gold medal at the short-course world championships in 2014 sparked some belief she could win over 50 metres.
"I'm so happy. Two years ago I was second, but now I'm the champion, so this is so important in my life," said Medeiros.
"I won a gold medal in 2014 in Doha, it was a tremendous experience and I'm sure that it helped me to achieve the reslt that I achieved today
"To win a world gold medal in a long course championship swimming with very competitive outstanding swimmers has a huge meaning.
"It is important for my country, my friends, my team and my colleagues in swimming. Brazilian swimming is becoming stronger.
"We got a silver in the men's relay, a silver in the 50m fly and 50m breaststroke and now with my medal in 50m back as well.
"We have been progressing and developing since 2015, there is still more competiton to be swum."
"I wasn't confident of winning after last night's semi-finals and the Chinese was very strong today.
"I was a bit nervous, but I took time to relax and just be happy and it worked out."