A stray female that he named Sochi passed away before getting to the U.S. for medical treatment, the silver medallist's friend Robin Macdonald announced on Twitter.
"No words can explain what has happened here, good bye little guy, we will miss you," along with a pic of him holding Sochi.
Macdonald, who'd stayed behind in Russia to finalize the paperwork for the mama dog and four pups that Kenworthy, 22, found on the streets of Sochi, explained in another Tweet that she died after authorities "refused to let me bring her to get treatment."
Macdonald and the remaining dogs – Jake, Rosa, Mishka, Mom and Stryder – set off for Denver on Tuesday.
Kenworthy said on Today last month that he planned to keep two of the puppies himself and another would go to his brother and his fiancé, and the mom would be adopted by Kenworthy's mother.
No words can explain what has happened here, good bye little guy, we will miss you. Heading home on Tuesday. pic.twitter.com/uAm8Naj2E0— Robin Macdonald (@robindmacdonald) March 9, 2014