Cindy Ord/Getty Images, Christopher Polk/Getty Images

Sounds like Kristen Stewart had a pretty happy MMMBirthday yesterday.

While their initial plan was for a low-key dinner party at home, the Twilight star and beau Robert Pattinson ended up at the bar No Vacancy at Hotel Juniper last night with a group of friends—where they happened to stumble upon a record release party for Hanson.

A source exclusively tells E! News that Rob and Kristen arrived at around 11 p.m. and spent time in both the main room and VIP area as part of a group of roughly a dozen people.

NEWS: See our 5 favorite Kristen Stewart looks 

“They weren’t overly affectionate or anything, but at points they were standing together as they talked to friends,” the source says.

It didn’t appear to be formal birthday party, with no one bringing out a cake or otherwise publicly marking Kristen’s big 2-3, but she and Rob were still there at 1 a.m.

Meanwhile, Nikki Reed and hubby Paul McDonald were also at No Vacancy, but the presence of the Twilight alumna may have been a coincidence, as she later posted a pic to Instagram of herself with Taylor Hanson.

“Get the Girl Back,” the first single off of Hanson’s upcoming album Anthem, dropped yesterday—hence the Hollywood celebration. It remains unclear, however, whether Robsten happen to be Hanson fans, or if they even knew that they were sharing party space with the trio.