After Taylor Swift got eight wins at the Billboard Music Awards in Las Vegas, Nevada last Sunday — and made her first public appearance with her new boyfriend, Calvin Harris, at the event — she and her good friend Ed Sheeran threw a party for the event's fellow attendees. 

It was reported that Adrian Grenier, David Guetta, Fifth Harmony, Jennifer Lopez, and Pentatonix were there, as well as One Direction members Niall Horan and Louis Tomlinson. Swift's younger brother Austin even shared a series of photo booth shots of him posing with his sister, Harris, Tomlinson, Sheeran, and Horan, which immediately went viral as fans once again took note of the "Bad Blood" singer's chemistry with the Scottish DJ. 

But notably absent that night was Harry Styles, who attended the Billboard Music Awards with his One Direction bandmates but was nowhere to be seen at the party.

One of the boy band's reps explained to E! News why Styles wasn't there, saying, "Harry didn't stay in Vegas after the awards, so [he] didn't attend any after-show party." 

It was rumored that Styles might be avoiding Swift that's why he failed to show up with Tomlinson and Horan at the fete. Styles dated the "Shake it Off" singer briefly from 2012 to 2013, and it is believed that he inspired several of the songs on her latest album "1989" including "Clean" and "Out of the Woods," although Swift never publicly identified who inspired her song lyrics. 

Meanwhile, an insider told Hollywood Life that Styles was invited to attend the party by Sheeran, but he turned it down.

"[Taylor and Harry] have a mutual friend in Ed Sheeran who has been trying to get all of them together to hang out," said the source. "Ed doesn't see any reason for them all not to be friends. He invited all of the One Direction boys and wanted Harry to join in, but Harry knew it would be awkward so he decided against it."