Seth took the stage Wednesday during The Hollywood Reporter’s Women in Entertainment Breakfast -- and true to form, he cracked a few jokes about folks in the audience.

A source with direct knowledge tells us, "The wrong event date was given to Kim’s team several weeks ago. The error was realized only on Monday and unfortunately, her schedule could not be moved around at the last minute due to a prior work commitment. She was incredibly disappointed to not be able to attend since she never cancels."

He joked, "Are we going to talk about how Kim Kardashian didn’t show up?" He continued, "I have seen every episode of ‘Keeping Up With the Kardashians’ I know she doesn’t have anything more important to do than this."

He made it clear it was all fun and games ... telling folks she was probably going through a lot and had good reason to skip.

Chelsea Handler also joked about the 'SKIMS' founder missing the event ... saying the extra security at the event wasn’t for Kim cause she didn’t show up.