ET caught up with the reality star "momager" at The Daily Front Row’s Fashion Los Angeles Awards on Sunday night, where she explained Khloe didn't make it to the big 2-9 family celebration because of work and illness.
"She was working and then she was sick and just had a crazy... yeah," Kris said. "I'm not even sure if she was working in or out of town. It's just so crazy."
Aww, we're sure Rob understood!
"We had a good time and we picked a night that most all of us could be in one place at the same time," Kris also noted.
Khloe confirmed as much about her not making it out on Saturday, tweeting, "The kiddies got me sick ??? feeling like sh*t today. Take your vitamins world."
Even sans his big sister, Rob and the rest of the clan appeared to have had a really sweet evening, which Kourtney documented on Instagram, writing, "Fams."
And although she couldn't make it, Khloe wish her brother happy birthday with a throwback photo on Instagram, writing, "Happy birthday to my ace @robkardashian!!! Forever my best friend!! I love and adore you!!."
Watch the video below for more from the occasion.